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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 217/239 problems.
+Solved 222/251 problems.
 
 ## Database
 
@@ -12,6 +12,11 @@ See [database.md](database.md)
 
 | # | Title | Solution |
 |---| ----- | -------- |
+|268|[Missing Number](/problems/missing-number/)|[missing-number.cc](missing-number.cc)|
+|264|[Ugly Number II](/problems/ugly-number-ii/)|[ugly-number-ii.cc](ugly-number-ii.cc)|
+|263|[Ugly Number](/problems/ugly-number/)|[ugly-number.cc](ugly-number.cc)|
+|258|[Add Digits](/problems/add-digits/)|[add-digits.cc](add-digits.cc)|
+|257|[Binary Tree Paths](/problems/binary-tree-paths/)|[binary-tree-paths.cc](binary-tree-paths.cc)|
 |242|[Valid Anagram](/problems/valid-anagram/)|[valid-anagram.cc](valid-anagram.cc)|
 |241|[Different Ways to Add Parentheses](/problems/different-ways-to-add-parentheses/)|[different-ways-to-add-parentheses.cc](different-ways-to-add-parentheses.cc)|
 |240|[Search a 2D Matrix II](/problems/search-a-2d-matrix-ii/)|[search-a-2d-matrix-ii.cc](search-a-2d-matrix-ii.cc)|

add-digits.cc

@@ -0,0 +1,7 @@
+// Add Digits
+class Solution {
+public:
+  int addDigits(int num) {
+    return num ? num%9 ? num%9 : 9 : 0;
+  }
+};

binary-tree-paths.cc

@@ -0,0 +1,17 @@
+// Binary Tree Paths
+class Solution {
+  vector<string> r;
+  void f(TreeNode *x, string s) {
+    if (! x) return;
+    s = s.empty() ? to_string(x->val) : s+"->"+to_string(x->val);
+    f(x->left, s);
+    f(x->right, s);
+    if (! x->left && ! x->right)
+      r.push_back(s);
+  }
+public:
+  vector<string> binaryTreePaths(TreeNode *root) {
+    f(root, "");
+    return r;
+  }
+};

missing-number.cc

@@ -0,0 +1,18 @@
+// Missing Number
+class Solution {
+public:
+  int missingNumber(vector<int> &a) {
+    int n = (int)a.size();
+    for (int i = 0; i < n; ) {
+      int j = a[i];
+      if (i != j && 0 <= j && j < n)
+        swap(a[i], a[j]);
+      else
+        i++;
+    }
+    for (int i = 0; i < n; i++)
+      if (a[i] != i)
+        return i;
+    return n;
+  }
+};

single-number-iii.cc

@@ -0,0 +1,12 @@
+// Single Number III
+class Solution {
+public:
+  vector<int> singleNumber(vector<int> &a) {
+    int k = accumulate(a.begin(), a.end(), 0, bit_xor<int>());
+    k &= -k;
+    return {
+      accumulate(a.begin(), a.end(), 0, [=](int s, int x) { return x & k ? s ^ x : s; }),
+      accumulate(a.begin(), a.end(), 0, [=](int s, int x) { return x & k ? s : s ^ x; })
+    };
+  }
+};

ugly-number-ii.cc

@@ -0,0 +1,16 @@
+// Ugly Number II
+class Solution {
+public:
+  int nthUglyNumber(int n) {
+    vector<int> a{1};
+    int i = 0, j = 0, k = 0;
+    while (a.size() < n) {
+      int x = min(min(a[i]*2, a[j]*3), a[k]*5);
+      a.push_back(x);
+      if (a[i]*2 == x) i++;
+      if (a[j]*3 == x) j++;
+      if (a[k]*5 == x) k++;
+    }
+    return a[n-1];
+  }
+};

ugly-number.cc

@@ -0,0 +1,12 @@
+// Ugly Number
+class Solution {
+public:
+  bool isUgly(int num) {
+    if (num) {
+      while (num % 2 == 0) num /= 2;
+      while (num % 3 == 0) num /= 3;
+      while (num % 5 == 0) num /= 5;
+    }
+    return num == 1;
+  }
+};