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atom.xml
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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title><![CDATA[Keep Hacking :)]]></title>
<link href="http://white1033.github.com/atom.xml" rel="self"/>
<link href="http://white1033.github.com/"/>
<updated>2013-04-20T11:16:56+08:00</updated>
<id>http://white1033.github.com/</id>
<author>
<name><![CDATA[Yen-Ying Lee]]></name>
</author>
<generator uri="http://octopress.org/">Octopress</generator>
<entry>
<title type="html"><![CDATA[初探Go]]></title>
<link href="http://white1033.github.com/blog/2013/03/17/lets-go/"/>
<updated>2013-03-17T17:00:00+08:00</updated>
<id>http://white1033.github.com/blog/2013/03/17/lets-go</id>
<content type="html"><![CDATA[<p>主要想學的原因是因為一些<a href="http://projecteuler.net/">ProjectEuler</a>的題目用<code>Ruby</code>或是<code>Perl</code>寫的時候，因為計算量太大，然後程式沒有辦法在一分鐘內跑完。</p>
<p>本來是想用之前學的<code>C/C++</code>來寫的，不過看到最近<code>golang</code>這麼熱，就來學一下啦！
先來記錄一些學習的資料</p>
<ul>
<li><a href="http://golang.org">官網</a></li>
<li><a href="http://godoc.org">GoDoc</a></li>
<li><a href="http://tour.golang.org/#1">A Tour of Go</a></li>
<li><a href="http://golang.org/doc/effective_go.html">Effective Go</a></li>
<li><a href="http://www.golang-book.com">An Introduction to Programming in Go</a></li>
<li><a href="https://github.com/astaxie/build-web-application-with-golang/blob/master/preface.md">用Go開發網頁應用</a></li>
</ul>
<p>這些應該夠我看一段時間了:)</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[從rvm轉換到rbenv]]></title>
<link href="http://white1033.github.com/blog/2013/03/10/from-rvm-to-rbenv/"/>
<updated>2013-03-10T01:16:00+08:00</updated>
<id>http://white1033.github.com/blog/2013/03/10/from-rvm-to-rbenv</id>
<content type="html"><![CDATA[<p>最近把用了一陣子的<code>rvm</code>給反安裝掉了，然後換成了<code>rbenv</code>來用用。會換過來的原因只是覺得<code>rbenv</code>比較輕量，而不是覺得<code>rvm</code>真的有什麼不好。</p>
<p>來記錄一下要怎麼轉換過來。</p>
<h2>反安裝rvm</h2>
<p>這個應該是最簡單的一步XD</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span>rvm implode
</span></code></pre></td></tr></table></div></figure>
<p>然後再將你<code>zsh</code>或<code>bash</code>中的這一句拿掉。</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="o">[[</span> -s <span class="s2">"$HOME/.rvm/scripts/rvm"</span> <span class="o">]]</span> <span class="o">&&</span> . <span class="s2">"$HOME/.rvm/scripts/rvm"</span> <span class="c"># Load RVM function</span>
</span></code></pre></td></tr></table></div></figure>
<!-- more -->
<h2>安裝rbenv</h2>
<p>我是透過<a href="http://mxcl.github.com/homebrew/">Homebrew</a>去安裝的。</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span>brew install rbenv
</span><span class='line'><span class="nv">$ </span>brew install ruby-build
</span></code></pre></td></tr></table></div></figure>
<p>要安裝<code>ruby-build</code>的原因是因為可以比較簡單的去安裝各個版本的ruby。</p>
<p>然後是把<code>~/.rbenv/bin</code>加到你的<code>$PATH</code>中。</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span><span class="nb">echo</span> <span class="s1">'export PATH="$HOME/.rbenv/bin:$PATH"'</span> >> ~/.zshrc
</span></code></pre></td></tr></table></div></figure>
<p>再來是將<code>rbenv init</code>加到你的shell中。</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span><span class="nb">echo</span> <span class="s1">'eval "$(rbenv init -)"'</span> >> ~/.zshrc
</span></code></pre></td></tr></table></div></figure>
<p>重新載入設定。</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span><span class="nb">source</span> ~/.zshrc
</span></code></pre></td></tr></table></div></figure>
<p>裝個好用的plugin <a href="https://github.com/tpope/rbenv-aliases">Aliases for rbenv Ruby versions</a></p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>mkdir -p ~/.rbenv/plugins
</span><span class='line'>git clone git://github.com/tpope/rbenv-aliases.git <span class="se">\</span>
</span><span class='line'> ~/.rbenv/plugins/rbenv-aliases
</span><span class='line'>rbenv <span class="nb">alias</span> --auto
</span></code></pre></td></tr></table></div></figure>
<p>最後當然是來裝個最新的ruby 2.0來玩玩:p</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span>rbenv install 2.0.0-p0
</span></code></pre></td></tr></table></div></figure>
<h2>基本指令</h2>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'><span class="nv">$ </span>rbenv install --list <span class="c">#列出所有可安裝版本</span>
</span><span class='line'><span class="nv">$ </span>rbenv versions <span class="c">#列出所有安裝的版本</span>
</span><span class='line'><span class="nv">$ </span>rbenv version <span class="c">#列出目前使用的版本</span>
</span><span class='line'><span class="nv">$ </span>rbenv global 2.0.0 <span class="c">#預設使用2.0.0</span>
</span><span class='line'><span class="nv">$ </span>rbenv shell 2.0.0 <span class="c">#在目前使用的shell使用 2.0.0</span>
</span><span class='line'><span class="nv">$ </span>rbenv <span class="nb">local </span>2.0.0 <span class="c">#在目前的資料夾使用 2.0.0</span>
</span></code></pre></td></tr></table></div></figure>
<p>先寫到這裡，之後有什麼心得再補上來。</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[一些Octopress的小技巧]]></title>
<link href="http://white1033.github.com/blog/2012/12/15/some-usefull-octopress-tips/"/>
<updated>2012-12-15T21:29:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/12/15/some-usefull-octopress-tips</id>
<content type="html"><![CDATA[<p>最近在發現了一些Octopress的小技巧，就放上來跟大家一同分享。</p>
<h3>上傳文章</h3>
<p>大家在上傳文章前必做的兩個指令就是</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>rake generate
</span><span class='line'>rake deploy</span></code></pre></td></tr></table></div></figure>
<p>不過它其實可以簡化成</p>
<figure class='code'><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class=''><span class='line'>rake gen_deploy</span></code></pre></td></tr></table></div></figure>
<p>就可以把兩個指令併成一個指令了！</p>
<!-- more -->
<h3>新增頁面</h3>
<p>之前都不知道要如何新增一個新的頁面出來，直到最近(遮臉)
其實就跟新增文章的指令一樣<code>new_post[your_post]</code>，新的頁面的指令就是<code>new_page[your_page]</code>，它就會產生一個makedown的檔案讓妳去編輯。之後妳需要做的就是將連結放到妳想要的地方了。</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Project Euler 61的解答]]></title>
<link href="http://white1033.github.com/blog/2012/10/14/project-euler-solution-061/"/>
<updated>2012-10-14T20:42:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/10/14/project-euler-solution-061</id>
<content type="html"><![CDATA[<p><a href="http://projecteuler.net/problem=61">題目</a>介紹了六種數列，分別是三角形數、四角形數、五角形數、六角形數、七角形數和八角形數。現在問題要找出來六個數字，分別在這六個數列中，而且可以頭尾相連連成一圈。網頁上有舉一個長度為四的數列，如果不懂的話可以去看看。</p>
<h2>做表查一下</h2>
<p>這題好像出奇的簡單啊啊啊啊，我的做法是把這六種數列的頭兩位數字做成一個表，然後用後兩位數去查有沒有合的數字，然後就一直查下去，直到有六個數字分別來自六個數列並頭尾相連成一圈。</p>
<!-- more -->
<p>附上程式碼：</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
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<span class='line-number'>40</span>
<span class='line-number'>41</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">#!/usr/bin/env ruby -wKU</span>
</span><span class='line'><span class="n">func</span> <span class="o">=</span> <span class="p">{</span>
</span><span class='line'> <span class="mi">3</span> <span class="o">=></span> <span class="o">-></span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="p">{</span><span class="n">x</span> <span class="o">*</span> <span class="p">(</span><span class="n">x</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span> <span class="o">/</span> <span class="mi">2</span><span class="p">},</span>
</span><span class='line'> <span class="mi">4</span> <span class="o">=></span> <span class="o">-></span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="p">{</span><span class="n">x</span> <span class="o">*</span> <span class="n">x</span><span class="p">},</span>
</span><span class='line'> <span class="mi">5</span> <span class="o">=></span> <span class="o">-></span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="p">{</span><span class="n">x</span> <span class="o">*</span> <span class="p">(</span><span class="mi">3</span> <span class="o">*</span> <span class="n">x</span> <span class="o">-</span> <span class="mi">1</span><span class="p">)</span> <span class="o">/</span> <span class="mi">2</span><span class="p">},</span>
</span><span class='line'> <span class="mi">6</span> <span class="o">=></span> <span class="o">-></span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="p">{</span><span class="n">x</span> <span class="o">*</span> <span class="p">(</span><span class="mi">2</span> <span class="o">*</span> <span class="n">x</span> <span class="o">-</span> <span class="mi">1</span><span class="p">)},</span>
</span><span class='line'> <span class="mi">7</span> <span class="o">=></span> <span class="o">-></span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="p">{</span><span class="n">x</span> <span class="o">*</span> <span class="p">(</span><span class="mi">5</span> <span class="o">*</span> <span class="n">x</span> <span class="o">-</span> <span class="mi">3</span><span class="p">)</span> <span class="o">/</span> <span class="mi">2</span><span class="p">},</span>
</span><span class='line'> <span class="mi">8</span> <span class="o">=></span> <span class="o">-></span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="p">{</span><span class="n">x</span> <span class="o">*</span> <span class="p">(</span><span class="mi">3</span> <span class="o">*</span> <span class="n">x</span> <span class="o">-</span> <span class="mi">2</span><span class="p">)}</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="n">n</span><span class="p">,</span> <span class="n">num</span><span class="p">,</span> <span class="vg">$type8</span> <span class="o">=</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="o">[]</span>
</span><span class='line'><span class="vg">$nums</span> <span class="o">=</span> <span class="no">Hash</span><span class="o">.</span><span class="n">new</span> <span class="p">{</span> <span class="o">|</span><span class="nb">hash</span><span class="p">,</span> <span class="n">key</span><span class="o">|</span> <span class="nb">hash</span><span class="o">[</span><span class="n">key</span><span class="o">]</span> <span class="o">=</span> <span class="o">[]</span> <span class="p">}</span>
</span><span class='line'><span class="k">while</span> <span class="kp">true</span>
</span><span class='line'> <span class="n">n</span> <span class="o">+=</span> <span class="mi">1</span>
</span><span class='line'> <span class="p">(</span><span class="mi">3</span> <span class="o">.</span><span class="n">.</span> <span class="mi">8</span><span class="p">)</span><span class="o">.</span><span class="n">reverse_each</span> <span class="k">do</span> <span class="o">|</span><span class="n">x</span><span class="o">|</span>
</span><span class='line'> <span class="n">num</span> <span class="o">=</span> <span class="n">func</span><span class="o">[</span><span class="n">x</span><span class="o">].</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
</span><span class='line'> <span class="k">if</span> <span class="p">(</span><span class="mi">1000</span> <span class="o">.</span><span class="n">.</span> <span class="mi">9999</span><span class="p">)</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="n">num</span><span class="p">)</span>
</span><span class='line'> <span class="k">if</span> <span class="n">x</span> <span class="o">==</span> <span class="mi">8</span>
</span><span class='line'> <span class="vg">$type8</span> <span class="o"><<</span> <span class="n">num</span>
</span><span class='line'> <span class="k">else</span>
</span><span class='line'> <span class="vg">$nums</span><span class="o">[</span><span class="n">num</span> <span class="o">/</span> <span class="mi">100</span><span class="o">]</span> <span class="o"><<</span> <span class="o">[</span><span class="n">num</span><span class="p">,</span> <span class="n">x</span><span class="o">]</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">break</span> <span class="k">if</span> <span class="n">num</span> <span class="o">></span> <span class="mi">9999</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">solve</span><span class="p">(</span><span class="n">num_set</span><span class="p">,</span> <span class="n">types</span><span class="p">)</span>
</span><span class='line'> <span class="k">if</span> <span class="n">types</span><span class="o">.</span><span class="n">size</span> <span class="o">==</span> <span class="mi">6</span>
</span><span class='line'> <span class="k">if</span> <span class="n">num_set</span><span class="o">[</span><span class="mi">0</span><span class="o">]</span> <span class="o">/</span> <span class="mi">100</span> <span class="o">==</span> <span class="n">num_set</span><span class="o">[-</span><span class="mi">1</span><span class="o">]</span> <span class="o">%</span> <span class="mi">100</span>
</span><span class='line'> <span class="nb">puts</span> <span class="n">num_set</span><span class="o">.</span><span class="n">reduce</span><span class="p">(</span><span class="ss">:+</span><span class="p">)</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">else</span>
</span><span class='line'> <span class="vg">$nums</span><span class="o">[</span><span class="n">num_set</span><span class="o">[-</span><span class="mi">1</span><span class="o">]</span> <span class="o">%</span> <span class="mi">100</span><span class="o">].</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">n</span><span class="o">|</span>
</span><span class='line'> <span class="k">unless</span> <span class="n">types</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="n">n</span><span class="o">[</span><span class="mi">1</span><span class="o">]</span><span class="p">)</span>
</span><span class='line'> <span class="n">solve</span><span class="p">(</span><span class="n">num_set</span> <span class="o">+</span> <span class="o">[</span><span class="n">n</span><span class="o">[</span><span class="mi">0</span><span class="o">]]</span><span class="p">,</span> <span class="n">types</span> <span class="o">+</span> <span class="o">[</span><span class="n">n</span><span class="o">[</span><span class="mi">1</span><span class="o">]]</span><span class="p">)</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'><span class="vg">$type8</span><span class="o">.</span><span class="n">each</span> <span class="p">{</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">solve</span><span class="p">(</span><span class="o">[</span><span class="n">e</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">8</span><span class="o">]</span><span class="p">)</span> <span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Project Euler 124的解答]]></title>
<link href="http://white1033.github.com/blog/2012/09/30/project-euler-solution-124/"/>
<updated>2012-09-30T13:29:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/09/30/project-euler-solution-124</id>
<content type="html"><![CDATA[<p><a href="http://projecteuler.net/problem=124">題目</a>是這樣說的，有一個函數叫做<code>rad</code>，它是去運算一個整數的所有的質因數的乘積。題目要問的就是請我們對<code>1~100000</code>中的數字用rad的大小做排序(如果rad一樣大，就再用數字的大小去做排序)之後，問排序後第10000的數字是誰？</p>
<h2>妳被迷惑了嗎？</h2>
<p>其實這題我們並不用去真的對數字去做排序，甚至也不用有個大質數表來做質因數分解:p</p>
<p>我的想法就是去推廣 <a href="http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes">Sieve of Eratosthenes</a>，但是不是將數字給刪除，反倒是將它建成一個表，去記錄她被哪些質數給整除過，然後在用rad的數字去建一個表，將rad值一樣的數字存入，最後在去算第10000的數字是誰就好了:D</p>
<!-- more -->
<p>附上程式碼：</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">#!/usr/bin/env ruby</span>
</span><span class='line'>
</span><span class='line'><span class="n">limit</span><span class="p">,</span> <span class="n">target</span> <span class="o">=</span> <span class="mi">100_000</span><span class="p">,</span> <span class="mi">10_000</span>
</span><span class='line'><span class="n">rad</span> <span class="o">=</span> <span class="no">Hash</span><span class="o">.</span><span class="n">new</span> <span class="p">{</span> <span class="o">|</span><span class="n">h</span><span class="p">,</span> <span class="n">k</span><span class="o">|</span> <span class="n">h</span><span class="o">[</span><span class="n">k</span><span class="o">]</span> <span class="o">=</span> <span class="mi">1</span> <span class="p">}</span>
</span><span class='line'><span class="n">cache</span> <span class="o">=</span> <span class="no">Hash</span><span class="o">.</span><span class="n">new</span> <span class="p">{</span> <span class="o">|</span><span class="n">h</span><span class="p">,</span> <span class="n">k</span><span class="o">|</span> <span class="n">h</span><span class="o">[</span><span class="n">k</span><span class="o">]</span> <span class="o">=</span> <span class="o">[]</span> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="p">(</span><span class="mi">2</span> <span class="o">.</span><span class="n">.</span> <span class="n">limit</span><span class="p">)</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">x</span><span class="o">|</span>
</span><span class='line'> <span class="k">if</span> <span class="n">rad</span><span class="o">[</span><span class="n">x</span><span class="o">]</span> <span class="o">==</span> <span class="mi">1</span>
</span><span class='line'> <span class="n">x</span><span class="o">.</span><span class="n">step</span><span class="p">(</span><span class="n">limit</span><span class="p">,</span> <span class="n">x</span><span class="p">)</span> <span class="p">{</span> <span class="o">|</span><span class="n">y</span><span class="o">|</span> <span class="n">rad</span><span class="o">[</span><span class="n">y</span><span class="o">]</span> <span class="o">*=</span> <span class="n">x</span> <span class="p">}</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="n">cache</span><span class="o">[</span><span class="n">rad</span><span class="o">[</span><span class="n">x</span><span class="o">]]</span> <span class="o"><<</span> <span class="n">x</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="n">cache</span><span class="o">.</span><span class="n">each_value</span> <span class="k">do</span> <span class="o">|</span><span class="n">v</span><span class="o">|</span>
</span><span class='line'> <span class="k">if</span> <span class="n">target</span> <span class="o"><=</span> <span class="n">v</span><span class="o">.</span><span class="n">size</span>
</span><span class='line'> <span class="nb">puts</span> <span class="n">v</span><span class="o">[</span><span class="n">target</span> <span class="o">-</span> <span class="mi">2</span><span class="o">]</span> <span class="c1">#ignore 1 </span>
</span><span class='line'> <span class="k">break</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="n">target</span> <span class="o">-=</span> <span class="n">v</span><span class="o">.</span><span class="n">size</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>
<p>這樣子就可以很快的算出答案了:D</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Project Euler 113的解答]]></title>
<link href="http://white1033.github.com/blog/2012/09/19/project-euler-solution-113/"/>
<updated>2012-09-19T22:19:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/09/19/project-euler-solution-113</id>
<content type="html"><![CDATA[<p><a href="http://projecteuler.net/problem=113">題目</a>是這樣說的，如果一個數字從左到右的各個位數是不嚴格遞增的話，那我們就說這種數字叫做遞增數，像是<code>134468</code>。反之，如果一個數字從左到右的各個位數是不嚴格遞減的話，那我們就說這種數字叫做遞減數，像是<code>66420</code>。如果一個數字從左到右的各個位數字，不是屬於上述的兩種狀況之一的話，我們就稱它是彈性數(Bouncy Number)。</p>
<p>現在問題來了，想要請問小於<code>10^100</code>中的數字中，有多少不是彈性數？</p>
<h2>高中排列組合</h2>
<p>好吧，這題其實不是太難，如果妳的高中數學沒有忘的話:)</p>
<p>遞增數的個數是<code>C(109, 9) - 1</code>，遞減數的個數是<code>C(110, 10) - 101</code>，又遞增又遞減的有<code>9 * 100</code>個，所以就只要寫個binomial的函數就可以了:D</p>
<!-- more -->
<p>附上程式碼：</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
</pre></td><td class='code'><pre><code class='perl'><span class='line'><span class="c1">#!/usr/bin/env perl</span>
</span><span class='line'><span class="k">use</span> <span class="n">v5</span><span class="mf">.12</span><span class="p">;</span>
</span><span class='line'><span class="k">use</span> <span class="n">warnings</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="k">sub </span><span class="nf">binomial</span> <span class="p">{</span>
</span><span class='line'> <span class="k">use</span> <span class="n">bigint</span><span class="p">;</span>
</span><span class='line'> <span class="k">my</span> <span class="p">(</span> <span class="nv">$r</span><span class="p">,</span> <span class="nv">$n</span><span class="p">,</span> <span class="nv">$k</span> <span class="p">)</span> <span class="o">=</span> <span class="p">(</span> <span class="mi">1</span><span class="p">,</span> <span class="nv">@_</span> <span class="p">);</span>
</span><span class='line'> <span class="nv">$r</span> <span class="o">=</span> <span class="nv">$r</span> <span class="o">*</span> <span class="p">(</span> <span class="nv">$n</span> <span class="o">+</span> <span class="mi">1</span> <span class="o">-</span> <span class="nv">$_</span> <span class="p">)</span> <span class="o">/</span> <span class="nv">$_</span> <span class="k">foreach</span> <span class="mi">1</span> <span class="o">..</span> <span class="nv">$k</span><span class="p">;</span>
</span><span class='line'> <span class="k">return</span> <span class="nv">$r</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="k">my</span> <span class="nv">$n</span> <span class="o">=</span> <span class="mi">100</span><span class="p">;</span>
</span><span class='line'><span class="n">say</span> <span class="n">binomial</span><span class="p">(</span> <span class="nv">$n</span> <span class="o">+</span> <span class="mi">9</span><span class="p">,</span> <span class="mi">9</span> <span class="p">)</span> <span class="o">-</span> <span class="mi">1</span> <span class="o">+</span> <span class="n">binomial</span><span class="p">(</span> <span class="nv">$n</span> <span class="o">+</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">10</span> <span class="p">)</span> <span class="o">-</span> <span class="mi">101</span> <span class="o">-</span> <span class="mi">9</span> <span class="o">*</span> <span class="nv">$n</span>
</span></code></pre></td></tr></table></div></figure>
<p>所以只要善用數學，題目還是可以用很簡單的方法解出來的:D</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Project Euler 90的解答]]></title>
<link href="http://white1033.github.com/blog/2012/09/09/project-euler-solution-090/"/>
<updated>2012-09-09T22:29:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/09/09/project-euler-solution-090</id>
<content type="html"><![CDATA[<p><a href="http://projecteuler.net/problem=90">題目</a>是這樣說的，有兩個六面骰子，同一個骰子的六個面的數字都不相同(但是不同顆可以有相同的數字)
然後骰子上來的數字都是來自<code>0~9</code>當中，問的是有幾種不同的骰子組合可以組出<code>01, 04, 09, ..., 81</code>，也就是所有的小於一百的平方數。</p>
<p>不過有一點要注意的就是說，題目提到可以將<code>6</code>和<code>9</code>混用，所以會比較多組答案。</p>
<h2>硬爆才是王道</h2>
<p>這題最直接的想法就是將所有的骰子的組合給拿出來檢驗，如果可以組出所有的平方數的話，就讓答案加一。</p>
<p>總之，實做上不難，讓我們直接來看程式碼吧！</p>
<!-- more -->
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">#!/usr/bin/env ruby</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">update_array</span><span class="p">(</span><span class="n">ary</span><span class="p">)</span>
</span><span class='line'> <span class="n">flag6</span> <span class="o">=</span> <span class="n">ary</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="mi">6</span><span class="p">)</span>
</span><span class='line'> <span class="n">flag9</span> <span class="o">=</span> <span class="n">ary</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="mi">9</span><span class="p">)</span>
</span><span class='line'> <span class="k">if</span> <span class="n">flag6</span> <span class="o">&&</span> <span class="n">flag9</span> <span class="o">||</span> <span class="o">!</span><span class="n">flag6</span> <span class="o">&&</span> <span class="o">!</span><span class="n">flag9</span>
</span><span class='line'> <span class="n">ary</span>
</span><span class='line'> <span class="k">elsif</span> <span class="n">flag6</span>
</span><span class='line'> <span class="n">ary</span> <span class="o"><<</span> <span class="mi">9</span>
</span><span class='line'> <span class="k">return</span> <span class="n">ary</span>
</span><span class='line'> <span class="k">elsif</span> <span class="n">flag9</span>
</span><span class='line'> <span class="n">ary</span> <span class="o"><<</span> <span class="mi">6</span>
</span><span class='line'> <span class="k">return</span> <span class="n">ary</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="n">square_dice</span> <span class="o">=</span>
</span><span class='line'> <span class="o">[[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">4</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">9</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">6</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">2</span><span class="p">,</span> <span class="mi">5</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">6</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">4</span><span class="p">,</span> <span class="mi">9</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">6</span><span class="p">,</span> <span class="mi">4</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mi">8</span><span class="p">,</span> <span class="mi">1</span><span class="o">]]</span>
</span><span class='line'><span class="n">ans</span> <span class="o">=</span> <span class="mi">0</span>
</span><span class='line'>
</span><span class='line'><span class="o">[*</span><span class="mi">0</span> <span class="o">.</span><span class="n">.</span> <span class="mi">9</span><span class="o">].</span><span class="n">combination</span><span class="p">(</span><span class="mi">6</span><span class="p">)</span><span class="o">.</span><span class="n">to_a</span><span class="o">.</span><span class="n">combination</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">ary1</span><span class="p">,</span> <span class="n">ary2</span><span class="o">|</span>
</span><span class='line'> <span class="n">ary1</span> <span class="o">=</span> <span class="n">update_array</span><span class="p">(</span><span class="n">ary1</span><span class="p">)</span>
</span><span class='line'> <span class="n">ary2</span> <span class="o">=</span> <span class="n">update_array</span><span class="p">(</span><span class="n">ary2</span><span class="p">)</span>
</span><span class='line'> <span class="n">flag</span> <span class="o">=</span> <span class="kp">true</span>
</span><span class='line'> <span class="n">square_dice</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="o">|</span>
</span><span class='line'> <span class="k">if</span> <span class="o">!</span><span class="p">(</span><span class="n">ary1</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="n">y</span><span class="p">)</span> <span class="o">&&</span> <span class="n">ary2</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="n">x</span><span class="p">))</span> <span class="o">&&</span>
</span><span class='line'> <span class="o">!</span><span class="p">(</span><span class="n">ary1</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="o">&&</span> <span class="n">ary2</span><span class="o">.</span><span class="n">include?</span><span class="p">(</span><span class="n">y</span><span class="p">))</span>
</span><span class='line'> <span class="n">flag</span> <span class="o">=</span> <span class="kp">false</span>
</span><span class='line'> <span class="k">break</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="n">ans</span> <span class="o">+=</span> <span class="mi">1</span> <span class="k">if</span> <span class="n">flag</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'><span class="nb">puts</span> <span class="n">ans</span>
</span></code></pre></td></tr></table></div></figure>
<p>實際上跑起來也是挺快的:P 看來因為組合數沒有很大的關係:)</p>
<p>BTW，這題是我在ProjectEuler上解的第一百五十題，呼~~</p>
<p>又往前多進了一步了:D</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Project Euler 92的解答]]></title>
<link href="http://white1033.github.com/blog/2012/09/01/project-euler-solution-092/"/>
<updated>2012-09-01T19:27:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/09/01/project-euler-solution-092</id>
<content type="html"><![CDATA[<p><a href="http://projecteuler.net/problem=92">題目</a>是這樣說的，妳只要將一個數字的各位數字平方後相加, 然後妳就一直重複這樣做，要嘛會停在1，不然就會掉到一個由89開頭的迴圈中(是有沒有這麼神奇！？)。</p>
<p>問題就是要去問說，在一千萬以下，有多少數字會跑到89？</p>
<h2>直觀的做法</h2>
<p>由於經過一次操作過後，數字和一定不會超過567，所以我們可以做一個表，然後去看在0到567中間的數字會停在1或者是89。之後在去檢查小於一千萬裡面的數，有多少會掉到會回到89的數裡面，就可以算出來答案了。</p>
<p>可是寫出來的程式跑的不是很快，讓人心情不是很好，所以就想了另一個演算法。</p>
<!-- more -->
<h2>改進過的做法</h2>
<p>後來想想，如果像是<code>1234567</code>的<code>7!</code>種組合，其實經過一次操作後，都會回到同一個數字，可是我之前的做法就會重複算了<code>7!</code>次，就會慢了許多，因為一直重複算一樣的東西。</p>
<p>所以新的做法，我是先去算出小於一千萬的數字經過一次操作後，所有可能的數字還有她們的組合數，然後再去看她們有多少會跑到89。</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
</pre></td><td class='code'><pre><code class='perl'><span class='line'><span class="c1">#!/usr/bin/env perl</span>
</span><span class='line'><span class="k">use</span> <span class="n">v5</span><span class="mf">.12</span><span class="p">;</span>
</span><span class='line'><span class="k">use</span> <span class="n">warnings</span><span class="p">;</span>
</span><span class='line'><span class="k">use</span> <span class="nn">List::</span><span class="n">Util</span> <span class="sx">qw(sum)</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'><span class="k">sub </span><span class="nf">to_1or89</span> <span class="p">{</span>
</span><span class='line'> <span class="k">my</span> <span class="nv">$x</span> <span class="o">=</span> <span class="nb">shift</span><span class="p">;</span>
</span><span class='line'> <span class="k">while</span> <span class="p">(</span> <span class="nv">$x</span> <span class="o">!=</span> <span class="mi">89</span> <span class="o">&&</span> <span class="nv">$x</span> <span class="o">!=</span> <span class="mi">1</span> <span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="nv">$x</span> <span class="o">=</span> <span class="n">sum</span><span class="p">(</span> <span class="nb">map</span> <span class="p">{</span> <span class="nv">$_</span> <span class="o">*</span> <span class="nv">$_</span> <span class="p">}</span> <span class="nb">split</span> <span class="sr">//</span><span class="p">,</span> <span class="nv">$x</span> <span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="k">return</span> <span class="nv">$x</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="k">my</span> <span class="nv">%hash</span> <span class="o">=</span> <span class="p">(</span> <span class="mi">0</span> <span class="o">=></span> <span class="mi">1</span> <span class="p">);</span>
</span><span class='line'><span class="k">my</span> <span class="nv">@squares</span> <span class="o">=</span> <span class="p">(</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">9</span><span class="p">,</span> <span class="mi">16</span><span class="p">,</span> <span class="mi">25</span><span class="p">,</span> <span class="mi">36</span><span class="p">,</span> <span class="mi">49</span><span class="p">,</span> <span class="mi">64</span><span class="p">,</span> <span class="mi">81</span> <span class="p">);</span>
</span><span class='line'><span class="k">foreach</span> <span class="p">(</span> <span class="mi">0</span> <span class="o">..</span> <span class="mi">6</span> <span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="k">my</span> <span class="nv">%tmp</span><span class="p">;</span>
</span><span class='line'> <span class="k">while</span> <span class="p">(</span> <span class="k">my</span> <span class="p">(</span> <span class="nv">$k</span><span class="p">,</span> <span class="nv">$v</span> <span class="p">)</span> <span class="o">=</span> <span class="nb">each</span> <span class="nv">%hash</span> <span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="nv">$tmp</span><span class="p">{</span> <span class="nv">$k</span> <span class="o">+</span> <span class="nv">$_</span> <span class="p">}</span> <span class="o">+=</span> <span class="nv">$v</span> <span class="k">foreach</span> <span class="nv">@squares</span><span class="p">;</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="nv">%hash</span> <span class="o">=</span> <span class="nv">%tmp</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="k">my</span> <span class="nv">%ans</span> <span class="o">=</span> <span class="p">(</span> <span class="mi">1</span> <span class="o">=></span> <span class="mi">0</span><span class="p">,</span> <span class="mi">89</span> <span class="o">=></span> <span class="mi">0</span> <span class="p">);</span>
</span><span class='line'><span class="nb">delete</span> <span class="nv">$hash</span><span class="p">{</span><span class="mi">0</span><span class="p">};</span>
</span><span class='line'><span class="k">while</span> <span class="p">(</span> <span class="k">my</span> <span class="p">(</span> <span class="nv">$k</span><span class="p">,</span> <span class="nv">$v</span> <span class="p">)</span> <span class="o">=</span> <span class="nb">each</span> <span class="nv">%hash</span> <span class="p">)</span> <span class="p">{</span>
</span><span class='line'> <span class="nv">$ans</span><span class="p">{</span> <span class="n">to_1or89</span><span class="p">(</span><span class="nv">$k</span><span class="p">)</span> <span class="p">}</span> <span class="o">+=</span> <span class="nv">$v</span><span class="p">;</span>
</span><span class='line'><span class="p">}</span>
</span><span class='line'><span class="n">say</span> <span class="nv">$ans</span><span class="p">{</span><span class="mi">89</span><span class="p">}</span>
</span></code></pre></td></tr></table></div></figure>
<p>這樣改寫後，速度有十分大的提升啊，不到一秒就算完了，看來之後這種題目還是多花一點心思想一下好了。</p>
<h3>其他資訊</h3>
<p>Happy Number:<a href="http://en.wikipedia.org/wiki/Happy_number">http://en.wikipedia.org/wiki/Happy_number</a></p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[玩Ruby Warrior學Ruby]]></title>
<link href="http://white1033.github.com/blog/2012/08/04/ruby-warrior/"/>
<updated>2012-08-04T17:19:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/08/04/ruby-warrior</id>
<content type="html"><![CDATA[<p>最近看到了這個<a href="http://vimeo.com/groups/rubytw/videos/29884753">影片</a>，上面談到了一個遊戲叫做<a href="https://github.com/ryanb/ruby-warrior/">Ruby Warrior</a>，說是可以藉由玩這個遊戲來學習<a href="http://www.ruby-lang.org/en/">Ruby</a>。</p>
<p>玩遊戲學Ruby，聽起來挺不錯的，不過要怎麼開始？</p>
<h2>開始玩吧！</h2>
<p>首先當然要把遊戲先裝起來啊！！先把Ruby Warrior的gem給裝一下</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
</pre></td><td class='code'><pre><code class='bash'><span class='line'>gem install rubywarrior
</span></code></pre></td></tr></table></div></figure>
<p>再來執行<code>rubywarrior</code>後，就可以新增帳號開始玩了！</p>
<!-- more -->
<h2>該怎麼玩啊？</h2>
<p>遊戲主要是藉由去修改<code>player.rb</code>，然後去執行<code>rubywarrior</code>後，看看妳寫的程式是否可以過關:)</p>
<p>一開始你會發現你的<code>player.rb</code>長的像這樣</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">class</span> <span class="nc">Player</span>
</span><span class='line'> <span class="k">def</span> <span class="nf">play_turn</span><span class="p">(</span><span class="n">warrior</span><span class="p">)</span>
</span><span class='line'> <span class="c1"># your code goes here</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>
<p>十分的乾淨… 不過幸好，第一關也是很簡單，只要一直向前走，就可以過關了:D
就像下面的這樣：</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">class</span> <span class="nc">Player</span>
</span><span class='line'> <span class="k">def</span> <span class="nf">play_turn</span><span class="p">(</span><span class="n">warrior</span><span class="p">)</span>
</span><span class='line'> <span class="n">warrior</span><span class="o">.</span><span class="n">walk!</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>
<p>這樣就可以過第一關了:D</p>
<p>不過我想這個遊戲的最大樂趣應該就是靠自己寫的程式過關吧:p
所以我也不多分享程式碼了，如果有卡關的再一同討論吧:D</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[初解八皇后問題]]></title>
<link href="http://white1033.github.com/blog/2012/03/24/first-glance-on-eight-queens-problem/"/>
<updated>2012-03-24T21:05:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/03/24/first-glance-on-eight-queens-problem</id>
<content type="html"><![CDATA[<p>這個其實是個很有名的問題，可是我直到最近才好好的(？)把這個題目給好好的做了一下。看來有人問問題還是比較有壓力快快的解出問題XD</p>
<h2>從西洋棋說起</h2>
<p>這是一個由西洋棋來的問題，問說是否可以找到一種放置八個皇后的方法，使得八個皇后不會相互吃到對方，也就是說整個棋盤會被八個皇后給蓋住。</p>
<p>在軍中的時候，其實有跟資工的同梯談過這個問題，他說這種題目通常有兩種重要的取向，一個是最快解出一組解，另一個是最快解出所有的解。</p>
<p>不過因為我用的語言不是C/C++，感覺也不用跟別人爭什麼最快，就開開心心的解就好了。</p>
<!-- more -->
<h2>八城堡問題？</h2>
<p>我在公車上想這個問題的時候，第一個跑入腦中的就是「八城堡問題」。我得說，可能真的找不到這個名字的問題，不過我覺得是個很好的簡化。</p>
<p>其實我們做的事情就是將皇后換成了城堡，不過這個問題就簡單很多了，因為只要是一個一到八的排列就是解答了。例如給出[1, 2, 3, 4, 5, 6, 7, 8]，就對應到(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), (8, 8)這八個點，很明顯就是個八城堡的解。我們得到了一組八城堡的解，也就快得到一組八皇后的解了，因為我們只要去看檢查對角線的方向，是不是有蓋到對方，就可以知道是不是一組八皇后的解了。</p>
<h2>解法</h2>
<p>有了想法，實現就不難，下面附上我的ruby寫法。</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">#!/usr/bin/env ruby</span>
</span><span class='line'><span class="nb">require</span> <span class="s2">"set"</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">layout</span><span class="p">(</span><span class="n">perm</span><span class="p">)</span>
</span><span class='line'> <span class="p">(</span><span class="mi">0</span> <span class="o">.</span><span class="n">.</span><span class="o">.</span> <span class="mi">8</span><span class="p">)</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">i</span><span class="o">|</span>
</span><span class='line'> <span class="n">perm</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">x</span><span class="o">|</span>
</span><span class='line'> <span class="nb">print</span> <span class="n">i</span> <span class="o">==</span> <span class="n">x</span> <span class="p">?</span> <span class="s1">' Q'</span> <span class="p">:</span> <span class="s1">' .'</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="nb">puts</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="nb">Array</span><span class="p">(</span><span class="mi">0</span> <span class="o">.</span><span class="n">.</span><span class="o">.</span> <span class="mi">8</span><span class="p">)</span><span class="o">.</span><span class="n">permutation</span><span class="p">(</span><span class="mi">8</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">perm</span><span class="o">|</span>
</span><span class='line'> <span class="k">if</span> <span class="nb">Array</span><span class="p">(</span><span class="mi">0</span> <span class="o">.</span><span class="n">.</span><span class="o">.</span> <span class="mi">8</span><span class="p">)</span><span class="o">.</span><span class="n">map</span> <span class="p">{</span> <span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="n">perm</span><span class="o">[</span><span class="n">i</span><span class="o">]</span> <span class="o">-</span> <span class="n">i</span> <span class="p">}</span><span class="o">.</span><span class="n">to_set</span><span class="o">.</span><span class="n">size</span> <span class="o">==</span> <span class="mi">8</span> <span class="o">&&</span>
</span><span class='line'> <span class="nb">Array</span><span class="p">(</span><span class="mi">0</span> <span class="o">.</span><span class="n">.</span><span class="o">.</span> <span class="mi">8</span><span class="p">)</span><span class="o">.</span><span class="n">map</span> <span class="p">{</span> <span class="o">|</span><span class="n">i</span><span class="o">|</span> <span class="n">perm</span><span class="o">[</span><span class="n">i</span><span class="o">]</span> <span class="o">+</span> <span class="n">i</span> <span class="p">}</span><span class="o">.</span><span class="n">to_set</span><span class="o">.</span><span class="n">size</span> <span class="o">==</span> <span class="mi">8</span>
</span><span class='line'> <span class="n">layout</span><span class="p">(</span><span class="n">perm</span><span class="p">)</span>
</span><span class='line'> <span class="k">break</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'><span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>
<p>果然是很輕鬆就解決了XD，希望還有寫出下一個更快速的解法的機會:P</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Project Euler 358的解答]]></title>
<link href="http://white1033.github.com/blog/2012/02/25/project-euler-solution-358/"/>
<updated>2012-02-25T14:47:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/02/25/project-euler-solution-358</id>
<content type="html"><![CDATA[<p>這題是在去設定Cluster的時候看到的，發現這題蠻簡單的，所以回家的時候就順手解了它。</p>
<p><a href="http://projecteuler.net/problem=358">題目</a>是這樣說的，有一種數叫做<a href="http://goo.gl/XVOjK">cyclic number</a>，仔細的性質大家就去看一下<a href="http://en.wikipedia.org/wiki/Main_Page">Wikipedia</a>上的介紹吧，這裡就不多加說明了。那麼題目要找的是一個開頭是<code>00000000137</code>，而結尾是<code>56789</code>的一個唯一的cyclic number，然後請我們算出它的數字和。</p>
<h2>從142857說起</h2>
<p>這個數字我是在高中的時候第一次聽到的，當時聽到的時候真是十分的驚訝，原來這世界上有這麼美的數字。</p>
<p>後來在學校的BBS裡面發現有很多更深入的討論，所以也對這種類型的數字有了一點點初步的了解。</p>
<p>BTW，在我大學的時候參加迎新宿營的時候，剛剛好也出了類似的題目，所以也就順手秒殺了XD，據說當時嚇到很多學長姐，因為他們本來想用這題來拖點時間的，結果沒有想到人算不如天算啊XDDD</p>
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<h2>回到正題</h2>
<p>那麼這題的解題關鍵是什麼呢？其實每一個cyclic number都會有一個跟它對應的分數(如果妳不知道，可以看看上面wiki的連結，裡面應該是會有講才是。)，像是<code>142857</code>對應的就是<code>1/7</code>:p</p>
<p>所以現在問題就變成找一個質數<code>p</code>使得下面的事情成立：</p>
<ul>
<li><code>1/p</code>它前面的位數是<code>0.00000000137</code></li>
<li><code>(10^(p - 1) - 1) / p</code>的後面幾位是<code>56789</code></li>
<li>再來我們只要去算<code>9 * (p - 1) / 2</code>就會是它的數字和了(wtf!?)</li>
</ul>
<p>前兩點聽起來很合理，但是第三點是什麼？為什麼這樣就可以算出來數字和呢？
原因是這樣的，我們知道<code>1/p</code>的循環節長度是<code>p-1</code>，而又因為<code>1/p + (p - 1)/p = 1 = 0.999...</code>，所以我們知道數字和就是<code>9 * (p - 1) / 2</code>，是不是很漂亮呢:p</p>
<p>下面附上程式碼：</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
</pre></td><td class='code'><pre><code class='python'><span class='line'><span class="c">#!/usr/bin/env python</span>
</span><span class='line'><span class="kn">from</span> <span class="nn">euler</span> <span class="kn">import</span> <span class="n">is_prime</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">is_primitive</span><span class="p">(</span><span class="n">num</span><span class="p">,</span> <span class="n">prime</span><span class="p">):</span>
</span><span class='line'> <span class="n">tmp</span> <span class="o">=</span> <span class="n">prime</span> <span class="o">-</span> <span class="mi">1</span>
</span><span class='line'> <span class="n">idx</span> <span class="o">=</span> <span class="mi">2</span>
</span><span class='line'> <span class="k">while</span> <span class="n">idx</span><span class="o">**</span><span class="mi">2</span> <span class="o"><=</span> <span class="n">tmp</span><span class="p">:</span>
</span><span class='line'> <span class="k">if</span> <span class="n">tmp</span> <span class="o">%</span> <span class="n">idx</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span>
</span><span class='line'> <span class="k">if</span> <span class="nb">pow</span><span class="p">(</span><span class="n">num</span><span class="p">,</span> <span class="n">idx</span><span class="p">,</span> <span class="n">prime</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span> <span class="ow">or</span> <span class="nb">pow</span><span class="p">(</span><span class="n">num</span><span class="p">,</span> <span class="n">tmp</span> <span class="o">/</span> <span class="n">idx</span><span class="p">,</span> <span class="n">prime</span><span class="p">)</span> <span class="o">==</span> <span class="mi">1</span><span class="p">:</span>
</span><span class='line'> <span class="k">return</span> <span class="bp">False</span>
</span><span class='line'> <span class="n">idx</span> <span class="o">+=</span> <span class="mi">1</span>
</span><span class='line'> <span class="k">return</span> <span class="bp">True</span>
</span><span class='line'>
</span><span class='line'><span class="n">upper_bound</span> <span class="o">=</span> <span class="mi">729927007</span>
</span><span class='line'><span class="n">lower_bound</span> <span class="o">=</span> <span class="mi">724709891</span>
</span><span class='line'>
</span><span class='line'><span class="k">for</span> <span class="n">num</span> <span class="ow">in</span> <span class="nb">xrange</span><span class="p">(</span><span class="n">lower_bound</span><span class="p">,</span> <span class="n">upper_bound</span><span class="p">,</span> <span class="mi">100000</span><span class="p">):</span>
</span><span class='line'> <span class="k">if</span> <span class="n">is_prime</span><span class="p">(</span><span class="n">num</span><span class="p">)</span> <span class="ow">and</span> <span class="n">is_primitive</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span> <span class="n">num</span><span class="p">):</span>
</span><span class='line'> <span class="k">print</span><span class="p">((</span><span class="n">num</span> <span class="o">-</span> <span class="mi">1</span><span class="p">)</span> <span class="o">*</span> <span class="mi">9</span> <span class="o">/</span> <span class="mi">2</span><span class="p">)</span>
</span></code></pre></td></tr></table></div></figure>
<p>真是美麗的一題，謝謝Project Euler:)</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Project Euler 206的解答]]></title>
<link href="http://white1033.github.com/blog/2012/01/29/project-euler-solution-206/"/>
<updated>2012-01-29T01:46:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/01/29/project-euler-solution-206</id>
<content type="html"><![CDATA[<p>其實是單純覺得這題蠻簡單的，而且一下就寫完了，所以就順手把它寫一下。</p>
<p><a href="http://projecteuler.net/problem=206">題目</a>是要找出一個唯一的正整數，使得它的平方長得要像<code>1_2_3_4_5_6_7_8_9_0</code>這種形式。因爲數字是平方數，不難判斷最後是<code>00</code>結尾，所以要判斷的地方就更少了一點。解决的方法是直接採用暴力法，從上界往回找，直到符合這個形式。</p>
<!-- more -->
<p>程式碼：</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">#!/usr/bin/env ruby</span>
</span><span class='line'>
</span><span class='line'><span class="n">upper_bound</span> <span class="o">=</span> <span class="mi">19_293_949_596_979_899</span>
</span><span class='line'><span class="n">upper_bound_sqrt</span> <span class="o">=</span> <span class="p">(</span><span class="no">Math</span><span class="o">.</span><span class="n">sqrt</span><span class="p">(</span><span class="n">upper_bound</span><span class="p">)</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">to_i</span>
</span><span class='line'>
</span><span class='line'><span class="k">while</span> <span class="kp">true</span>
</span><span class='line'> <span class="k">break</span> <span class="k">if</span> <span class="p">(</span><span class="n">upper_bound_sqrt</span><span class="o">**</span><span class="mi">2</span><span class="p">)</span><span class="o">.</span><span class="n">to_s</span><span class="o">.</span><span class="n">match</span><span class="p">(</span><span class="sr">/1.2.3.4.5.6.7.8.9/</span><span class="p">)</span>
</span><span class='line'> <span class="n">upper_bound_sqrt</span> <span class="o">-=</span> <span class="mi">2</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="nb">puts</span> <span class="n">upper_bound_sqrt</span> <span class="o">*</span> <span class="mi">10</span>
</span></code></pre></td></tr></table></div></figure>
<p>本來還想對做平方的數字做最佳化，其實奇數也只有3跟9的平方尾數會是9，但是没有最佳化的程式就跑得夠快了，所以就懶得最佳化了:p</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[有趣的猜數字謎題]]></title>
<link href="http://white1033.github.com/blog/2012/01/25/guessing-number-puzzle/"/>
<updated>2012-01-25T14:46:00+08:00</updated>
<id>http://white1033.github.com/blog/2012/01/25/guessing-number-puzzle</id>
<content type="html"><![CDATA[<p>這種題目感覺就是百出不厭，一些公司的面試題也會出現，不過解起來也是十分有趣:D</p>
<h2>題目</h2>
<p>老師心中想了一個兩位數。他把這兩位數的兩個數字和告訴了A，把這個兩位數的正因數個數告訴了B。</p>
<p>A：我不知道。</p>
<p>B：我也不知道, 但我知道是否為偶數。</p>
<p>A：我知道了。</p>
<p>B：我也知道了。</p>
<p>請問此兩位數是誰？</p>
<p>以前自己做這種題目，都是拿著筆一個一個慢慢淘汰，不過今天要選擇用把我的解題邏輯寫成程式碼，讓電腦幫我做淘汰這件事情:p</p>
<!-- more -->
<p>附上我的程式碼跟解題邏輯：</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
<span class='line-number'>35</span>
<span class='line-number'>36</span>
<span class='line-number'>37</span>
<span class='line-number'>38</span>
<span class='line-number'>39</span>
<span class='line-number'>40</span>
<span class='line-number'>41</span>
<span class='line-number'>42</span>
<span class='line-number'>43</span>
<span class='line-number'>44</span>
<span class='line-number'>45</span>
<span class='line-number'>46</span>
<span class='line-number'>47</span>
<span class='line-number'>48</span>
<span class='line-number'>49</span>
<span class='line-number'>50</span>
<span class='line-number'>51</span>
<span class='line-number'>52</span>
<span class='line-number'>53</span>
<span class='line-number'>54</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">#!/usr/bin/env ruby</span>
</span><span class='line'>
</span><span class='line'><span class="vg">$digit_sum_hash</span> <span class="o">=</span> <span class="no">Hash</span><span class="o">.</span><span class="n">new</span> <span class="p">{</span> <span class="o">|</span><span class="nb">hash</span><span class="p">,</span> <span class="n">key</span><span class="o">|</span> <span class="nb">hash</span><span class="o">[</span><span class="n">key</span><span class="o">]</span> <span class="o">=</span> <span class="o">[]</span> <span class="p">}</span>
</span><span class='line'><span class="vg">$div_num_hash</span> <span class="o">=</span> <span class="no">Hash</span><span class="o">.</span><span class="n">new</span> <span class="p">{</span> <span class="o">|</span><span class="nb">hash</span><span class="p">,</span> <span class="n">key</span><span class="o">|</span> <span class="nb">hash</span><span class="o">[</span><span class="n">key</span><span class="o">]</span> <span class="o">=</span> <span class="o">[]</span> <span class="p">}</span>
</span><span class='line'><span class="vg">$num_list</span> <span class="o">=</span> <span class="p">(</span><span class="mi">10</span> <span class="o">.</span><span class="n">.</span> <span class="mi">99</span><span class="p">)</span><span class="o">.</span><span class="n">to_a</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">sum_of_digit</span><span class="p">(</span><span class="n">num</span><span class="p">)</span>
</span><span class='line'> <span class="k">return</span> <span class="n">num</span><span class="o">.</span><span class="n">to_s</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="sr">//</span><span class="p">)</span><span class="o">.</span><span class="n">map</span><span class="p">(</span><span class="o">&</span><span class="ss">:to_i</span><span class="p">)</span><span class="o">.</span><span class="n">inject</span><span class="p">(</span><span class="ss">:+</span><span class="p">)</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">num_of_div</span><span class="p">(</span><span class="n">num</span><span class="p">)</span>
</span><span class='line'> <span class="n">ans</span> <span class="o">=</span> <span class="mi">0</span>
</span><span class='line'> <span class="p">(</span><span class="mi">1</span> <span class="o">.</span><span class="n">.</span> <span class="n">num</span><span class="p">)</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span>
</span><span class='line'> <span class="n">ans</span> <span class="o">+=</span> <span class="mi">1</span> <span class="k">if</span> <span class="n">num</span> <span class="o">%</span> <span class="n">e</span> <span class="o">==</span> <span class="mi">0</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'> <span class="k">return</span> <span class="n">ans</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="vg">$num_list</span><span class="o">.</span><span class="n">each</span> <span class="k">do</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span>
</span><span class='line'> <span class="vg">$digit_sum_hash</span><span class="o">[</span><span class="n">sum_of_digit</span><span class="p">(</span><span class="n">e</span><span class="p">)</span><span class="o">].</span><span class="n">push</span><span class="p">(</span><span class="n">e</span><span class="p">)</span>
</span><span class='line'> <span class="vg">$div_num_hash</span><span class="o">[</span><span class="n">num_of_div</span><span class="p">(</span><span class="n">e</span><span class="p">)</span><span class="o">].</span><span class="n">push</span><span class="p">(</span><span class="n">e</span><span class="p">)</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">first_step</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
</span><span class='line'> <span class="k">return</span> <span class="vg">$digit_sum_hash</span><span class="o">[</span><span class="n">sum_of_digit</span><span class="p">(</span><span class="n">n</span><span class="p">)</span><span class="o">].</span><span class="n">length</span> <span class="o">>=</span> <span class="mi">2</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">second_step</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
</span><span class='line'> <span class="n">subset</span> <span class="o">=</span> <span class="vg">$div_num_hash</span><span class="o">[</span><span class="n">num_of_div</span><span class="p">(</span><span class="n">n</span><span class="p">)</span><span class="o">].</span><span class="n">select</span> <span class="p">{</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">first_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="p">}</span>
</span><span class='line'> <span class="k">return</span> <span class="n">subset</span><span class="o">.</span><span class="n">length</span> <span class="o">>=</span> <span class="mi">2</span> <span class="o">&&</span>
</span><span class='line'> <span class="p">(</span><span class="n">subset</span><span class="o">.</span><span class="n">all?</span> <span class="p">{</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">e</span><span class="o">.</span><span class="n">even?</span> <span class="p">}</span> <span class="o">||</span> <span class="n">subset</span><span class="o">.</span><span class="n">all?</span> <span class="p">{</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="o">!</span><span class="p">(</span><span class="n">e</span><span class="o">.</span><span class="n">even?</span><span class="p">)</span> <span class="p">})</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">third_step</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
</span><span class='line'> <span class="n">subset</span> <span class="o">=</span> <span class="vg">$digit_sum_hash</span><span class="o">[</span><span class="n">sum_of_digit</span><span class="p">(</span><span class="n">n</span><span class="p">)</span><span class="o">].</span><span class="n">select</span> <span class="p">{</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span> <span class="n">second_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="p">}</span>
</span><span class='line'> <span class="k">return</span> <span class="p">(</span><span class="n">subset</span><span class="o">.</span><span class="n">length</span> <span class="o">==</span> <span class="mi">1</span><span class="p">)</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">forth_step</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
</span><span class='line'> <span class="n">subset</span> <span class="o">=</span> <span class="vg">$div_num_hash</span><span class="o">[</span><span class="n">num_of_div</span><span class="p">(</span><span class="n">n</span><span class="p">)</span><span class="o">].</span><span class="n">select</span> <span class="p">{</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span>
</span><span class='line'> <span class="n">first_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="o">&&</span> <span class="n">third_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="k">return</span> <span class="p">(</span><span class="n">subset</span><span class="o">.</span><span class="n">length</span> <span class="o">==</span> <span class="mi">1</span><span class="p">)</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="k">def</span> <span class="nf">final_step</span>
</span><span class='line'> <span class="n">subset</span> <span class="o">=</span> <span class="vg">$num_list</span><span class="o">.</span><span class="n">select</span> <span class="p">{</span> <span class="o">|</span><span class="n">e</span><span class="o">|</span>
</span><span class='line'> <span class="n">first_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="o">&&</span> <span class="n">second_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="o">&&</span>
</span><span class='line'> <span class="n">third_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span> <span class="o">&&</span> <span class="n">forth_step</span><span class="p">(</span><span class="n">e</span><span class="p">)</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="k">return</span> <span class="n">subset</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="nb">p</span> <span class="n">final_step</span><span class="p">()</span>
</span></code></pre></td></tr></table></div></figure>
<p>程式碼很多地方没有最佳化，因爲數字都還蠻小的(遮臉)，如果有更好的寫法，還請不吝指教一下:D</p>
<p>解題邏輯也很直觀，就照着對話依序删减可能的數字，最後一步就會跑出唯一的解答。</p>