373

Author: MaskRay

README.md

@@ -2,7 +2,7 @@
 
 [LeetCode solutions](http://maskray.me/blog/2014-06-29-leetcode-solutions) gives some thoughts on selected problems.
 
-Solved 368/368 problems.
+Solved 373/373 problems.
 
 ## Database
 
@@ -12,6 +12,11 @@ See [database.md](database.md)
 
 | # | Title | Solution |
 |---| ----- | -------- |
+|391|[Perfect Rectangle](https://leetcode.com/problems/perfect-rectangle/)|[perfect-rectangle.cc](perfect-rectangle.cc)|
+|389|[Find the Difference](https://leetcode.com/problems/find-the-difference/)|[find-the-difference.cc](find-the-difference.cc)|
+|388|[Longest Absolute File Path](https://leetcode.com/problems/longest-absolute-file-path/)|[longest-absolute-file-path.cc](longest-absolute-file-path.cc)|
+|387|[First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/)|[first-unique-character-in-a-string.cc](first-unique-character-in-a-string.cc)|
+|386|[Lexicographical Numbers](https://leetcode.com/problems/lexicographical-numbers/)|[lexicographical-numbers.cc](lexicographical-numbers.cc)|
 |385|[Mini Parser](https://leetcode.com/problems/mini-parser/)|[mini-parser.cc](mini-parser.cc)|
 |384|[Shuffle an Array](https://leetcode.com/problems/shuffle-an-array/)|[shuffle-an-array.cc](shuffle-an-array.cc)|
 |383|[Ransom Note](https://leetcode.com/problems/ransom-note/)|[ransom-note.cc](ransom-note.cc)|

find-the-difference.cc

@@ -0,0 +1,10 @@
+// Find the Difference
+class Solution {
+public:
+  char findTheDifference(string s, string t) {
+    long x = 0;
+    for (char i: t) x ^= i;
+    for (char i: s) x ^= i;
+    return x;
+  }
+};

first-unique-character-in-a-string.cc

@@ -0,0 +1,13 @@
+// First Unique Character in a String
+class Solution {
+public:
+  int firstUniqChar(string s) {
+    int a[26] = {}, i = 0;
+    for (char c: s)
+      a[c-'a']++;
+    for (; i < s.size(); i++)
+      if (a[s[i]-'a'] == 1)
+        return i;
+    return -1;
+  }
+};

lexicographical-numbers.cc

@@ -0,0 +1,19 @@
+// Lexicographical Numbers
+class Solution {
+public:
+  vector<int> lexicalOrder(int n) {
+    vector<int> r;
+    r.push_back(1);
+    for (int x = 1, i = 1; i < n; i++) {
+      if (x*10 <= n)
+        x *= 10;
+      else {
+        while (x == n || x%10 == 9)
+          x /= 10;
+        x++;
+      }
+      r.push_back(x);
+    }
+    return r;
+  }
+};

longest-absolute-file-path.cc

@@ -0,0 +1,21 @@
+// Longest Absolute File Path
+class Solution {
+public:
+  int lengthLongestPath(string input) {
+    vector<int> st;
+    int r = 0;
+    for (int j, i = 0; i < input.size(); i = j+1) {
+      char dot = 0;
+      for (j = i; j < input.size() && input[j] != '\n'; j++)
+        dot |= input[j] == '.';
+      int t = 0;
+      for (; input[i] == '\t'; i++)
+        t++;
+      st.resize(t);
+      st.push_back((st.empty() ? 0 : st.back()+1)+j-i);
+      if (dot)
+        r = max(r, st.back());
+    }
+    return r;
+  }
+};

perfect-rectangle.cc

@@ -0,0 +1,70 @@
+// Perfect Rectangle
+namespace std {
+template<>
+  struct hash<pair<int, int>> {
+    size_t operator()(const pair<int, int>& x) const {
+      return size_t(x.first) << 32 | x.second;
+    }
+  };
+};
+
+class Solution {
+public:
+  bool isRectangleCover(vector<vector<int>>& rectangles) {
+    int x0 = INT_MAX, x1 = INT_MIN, y0 = INT_MAX, y1 = INT_MIN;
+    unordered_map<pair<int, int>, int> m;
+    for (auto& a: rectangles) {
+      x0 = min(x0, a[0]);
+      y0 = min(y0, a[1]);
+      x1 = max(x1, a[2]);
+      y1 = max(y1, a[3]);
+      int& m1 = m[make_pair(a[0], a[1])]; if (m1 & 1) return false; m1 |= 1;
+      int& m2 = m[make_pair(a[0], a[3])]; if (m2 & 2) return false; m2 |= 2;
+      int& m4 = m[make_pair(a[2], a[3])]; if (m4 & 4) return false; m4 |= 4;
+      int& m8 = m[make_pair(a[2], a[1])]; if (m8 & 8) return false; m8 |= 8;
+    }
+    for (auto& i: m) {
+      int x, y, mask = i.second;
+      tie(x, y) = i.first;
+      if ((x == x0 || x == x1) && (y == y0 || y == y1)) {
+        if (__builtin_popcount(mask) != 1)
+          return false;
+      } else {
+        if (mask != 3 && mask != 6 && mask != 12 && mask != 9 && mask != 15)
+          return false;
+      }
+    }
+    return true;
+  }
+};
+
+/// sweep line
+
+class Solution {
+public:
+  bool isRectangleCover(vector<vector<int>>& rectangles) {
+    long area = 0, x0 = INT_MAX, x1 = INT_MIN, y0 = INT_MAX, y1 = INT_MIN;
+    vector<pair<int, pair<int, int>>> b;
+    set<pair<int, int>> active;
+    for (auto& a: rectangles) {
+      x0 = min(x0, long(a[0]));
+      y0 = min(y0, long(a[1]));
+      x1 = max(x1, long(a[2]));
+      y1 = max(y1, long(a[3]));
+      area += (long(a[2])-a[0])*(long(a[3])-a[1]);
+      b.emplace_back(a[0]*2+1, make_pair(a[1], a[3]));
+      b.emplace_back(a[2]*2, make_pair(a[1], a[3]));
+    }
+    sort(b.begin(), b.end());
+    for (auto& a: b)
+      if (a.first % 2) {
+        auto it = active.lower_bound(a.second);
+        if (it != active.begin() && a.second.first < prev(it)->second ||
+            it != active.end() && it->first < a.second.second)
+          return false;
+        active.insert(it, a.second);
+      } else
+        active.erase(a.second);
+    return area == (x1-x0)*(y1-y0);
+  }
+};