From 68f3a453e1e78530b10e78487d976650c8f295d8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=B4=AA=E9=88=9E=E9=96=94=20=28=20jasper=20=29?=
 <61868459+junminhong@users.noreply.github.com>
Date: Tue, 30 Apr 2024 15:58:47 +0800
Subject: [PATCH] feat: add ruby code block - merge sort (#1260)

* feat(codes/ruby/chapter_sorting/merge_sort.rb): add merge_sort ruby file

* feat(codes/ruby/chapter_sorting/merge_sort.rb): modify comment space

* feat(codes/ruby/chapter_sorting/merge_sort.rb): set array default value

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>

* feat(codes/ruby/chapter_sorting/merge_sort.rb): driver code add if logic

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>

* feat(codes/ruby/chapter_sorting/merge_sort.rb): modify comment style

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>

* feat(codes/ruby/chapter_sorting/merge_sort.rb): modify logic instruction

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>

---------

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>
---
 codes/ruby/chapter_sorting/merge_sort.rb | 60 ++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 codes/ruby/chapter_sorting/merge_sort.rb

diff --git a/codes/ruby/chapter_sorting/merge_sort.rb b/codes/ruby/chapter_sorting/merge_sort.rb
new file mode 100644
index 0000000000..2e90dd8951
--- /dev/null
+++ b/codes/ruby/chapter_sorting/merge_sort.rb
@@ -0,0 +1,60 @@
+=begin
+File: merge_sort.rb
+Created Time: 2024-04-10
+Author: junminhong (junminhong1110@gmail.com)
+=end
+
+### 合并左子数组和右子数组 ###
+def merge(nums, left, mid, right)
+  # 左子数组区间为 [left, mid], 右子数组区间为 [mid+1, right]
+  # 创建一个临时数组 tmp，用于存放合并后的结果
+  tmp = Array.new(right - left + 1, 0)
+  # 初始化左子数组和右子数组的起始索引
+  i, j, k = left, mid + 1, 0
+  # 当左右子数组都还有元素时，进行比较并将较小的元素复制到临时数组中
+  while i <= mid && j <= right
+    if nums[i] <= nums[j]
+      tmp[k] = nums[i]
+      i += 1
+    else
+      tmp[k] = nums[j]
+      j += 1
+    end
+    k += 1
+  end
+  # 将左子数组和右子数组的剩余元素复制到临时数组中
+  while i <= mid
+    tmp[k] = nums[i]
+    i += 1
+    k += 1
+  end
+  while j <= right
+    tmp[k] = nums[j]
+    j += 1
+    k += 1
+  end
+  # 将临时数组 tmp 中的元素复制回原数组 nums 的对应区间
+  (0...tmp.length).each do |k|
+    nums[left + k] = tmp[k]
+  end
+end
+
+### 归并排序 ###
+def merge_sort(nums, left, right)
+  # 终止条件
+  # 当子数组长度为 1 时终止递归
+  return if left >= right
+  # 划分阶段
+  mid = (left + right) / 2 # 计算中点
+  merge_sort(nums, left, mid) # 递归左子数组
+  merge_sort(nums, mid + 1, right) # 递归右子数组
+  # 合并阶段
+  merge(nums, left, mid, right)
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  nums = [7, 3, 2, 6, 0, 1, 5, 4]
+  merge_sort(nums, 0, nums.length - 1)
+  puts "归并排序完成后 nums = #{nums.inspect}"
+end