Updates hard/57.md

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Author: Ruby Chi

README.md

@@ -6,14 +6,14 @@ Here illustrate the problems I solved using JavaScript on [LeetCode](https://lee
 
 You can browse the entire document [here](https://rubychi1.gitbooks.io/leetcode/)
 
-## 73/656 Solved
+## 81/656 Solved
 
-* [Easy \(71\)](/easy.md)
+* [Easy \(79\)](/easy.md)
 
 * [Medium \(1\)](/medium.md)
 
 * [Hard \(1\)](/hard.md)
 
-<hr/>
+---
 
-*Last updated on Fri Sep 22 2017 23:14:24 GMT+0800*
+*Last updated on Sun Sep 24 2017 00:44:37 GMT+0800*

SUMMARY.md

@@ -3,8 +3,10 @@
 * [Introduction](README.md)
 * [Easy](easy.md)
   * [13. Roman to Integer](easy/13.md)
+  * [70. Climbing Stairs](easy/70.md)
   * [100. Same Tree](easy/100.md)
   * [104. Maximum Depth of Binary Tree](easy/104.md)
+  * [107. Binary Tree Level Order Traversal II ](easy/107.md)
   * [108. Convert Sorted Array to Binary Search Tree](easy/108.md)
   * [121. Best Time to Buy and Sell Stock](easy/121.md)
   * [122. Best Time to Buy and Sell Stock II](easy/122.md)
@@ -13,15 +15,18 @@
   * [168. Excel Sheet Column Title](easy/168.md)
   * [169. Majority Element](easy/169.md)
   * [171. Excel Sheet Column Number](easy/171.md)
+  * [202. Happy Number](easy/202.md)
   * [206. Reverse Linked List](easy/206.md)
   * [217. Contains Duplicate](easy/217.md)
   * [226. Invert Binary Tree](easy/226.md)
+  * [231. Power of Two](easy/231.md)
   * [237. Delete Node in a Linked List](easy/237.md)
   * [242. Valid Anagram](easy/242.md)
   * [258. Add Digits](easy/258.md)
   * [268. Missing Number](easy/268.md)
   * [283. Move Zeroes](easy/283.md)
   * [292. Nim Game](easy/292.md)
+  * [326. Power of Three](easy/326.md)
   * [344. Reverse String](easy/344.md)
   * [349. Intersection of Two Arrays](easy/349.md)
   * [350. Intersection of Two Arrays II](easy/350.md)
@@ -60,13 +65,16 @@
   * [561. Array Partition I](easy/561.md)
   * [563. Binary Tree Tilt](easy/563.md)
   * [566. Reshape the Matrix](easy/566.md)
+  * [572. Subtree of Another Tree](easy/572.md)
   * [575. Distribute Candies](easy/575.md)
+  * [594. Longest Harmonious Subsequence](easy/594.md)
   * [598. Range Addition II](easy/598.md)
   * [599. Minimum Index Sum of Two Lists](easy/599.md)
   * [606. Construct String from Binary Tree](easy/606.md)
   * [617. Merge Two Binary Trees](easy/617.md)
   * [628. Maximum Product of Three Numbers](easy/628.md)
   * [637. Average of Levels in Binary Tree](easy/637.md)
+  * [645. Set Mismatch](easy/645.md)
   * [653. Two Sum IV - Input is a BST](easy/653.md)
   * [657. Judge Route Circle](easy/657.md)
   * [669. Trim a Binary Search Tree](easy/669.md)

easy.md

@@ -5,8 +5,10 @@
 | \# | Title | Acceptance |
 | :--- | :--- | :--- |
 | 13 | [Roman to Integer](/easy/13.md) | 45.9% |
+| 70 | [Climbing Stairs](/easy/70.md) | 40.2% |
 | 100 | [Same Tree](/easy/100.md) | 46.6% |
 | 104 | [Maximum Depth of Binary Tree](/easy/104.md) | 52.7% |
+| 107 | [Binary Tree Level Order Traversal II](/easy/107.md) | 40.6% |
 | 108 | [Convert Sorted Array to Binary Search Tree](/easy/108.md) | 42.4% |
 | 121 | [Best Time to Buy and Sell Stock](/easy/121.md) | 41.3% |
 | 122 | [Best Time to Buy and Sell Stock II](/easy/122.md) | 47.1% |
@@ -15,15 +17,18 @@
 | 168 | [Excel Sheet Column Title](/easy/168.md) | 26.1% |
 | 169 | [Majority Element](/easy/169.md) | 46.7% |
 | 171 | [Excel Sheet Column Number](/easy/171.md) | 47.2% |
+| 202 | [Happy Number](/easy/202.md) | 40.8% |
 | 206 | [Reverse Linked List](/easy/206.md) | 45.5% |
 | 217 | [Contains Duplicate](/easy/217.md) | 45.9% |
 | 226 | [Invert Binary Tree](/easy/226.md) | 51.9% |
+| 231 | [Power of Two](/easy/231.md) | 40.3% |
 | 237 | [Delete Node in a Linked List](/easy/237.md) | 46.6% |
 | 242 | [Valid Anagram](/easy/242.md) | 46.5% |
 | 258 | [Add Digits](/easy/258.md) | 51.2% |
 | 268 | [Missing Number](/easy/268.md) | 44.3% |
 | 283 | [Move Zeroes](/easy/283.md) | 50.0% |
 | 292 | [Nim Game](/easy/292.md) | 55.2% |
+| 326 | [Power of Three](/easy/326.md) | 40.3% |
 | 344 | [Reverse String](/easy/344.md) | 59.2% |
 | 349 | [Intersection of Two Arrays](/easy/349.md) | 47.3% |
 | 350 | [Intersection of Two Arrays II](/easy/350.md) | 44.7% |
@@ -62,13 +67,16 @@
 | 561 | [Array Partition I](/easy/561.md) | 67.1% |
 | 563 | [Binary Tree Tilt](/easy/563.md) | 46.8% |
 | 566 | [Reshape the Matrix](/easy/566.md) | 59.1% |
+| 572 | [Subtree of Another Tree](/easy/572.md) | 40.7% |
 | 575 | [Distribute Candies](/easy/575.md) | 59.2% |
+| 594 | [Longest Harmonious Subsequence](/easy/594.md) | 40.8% |
 | 598 | [Range Addition II](/easy/598.md) | 48.1% |
 | 599 | [Minimum Index Sum of Two Lists](/easy/599.md) | 46.8% |
 | 606 | [Construct String from Binary Tree](/easy/606.md) | 50.1% |
 | 617 | [Merge Two Binary Trees](/easy/617.md) | 68.3% |
 | 628 | [Maximum Product of Three Numbers](/easy/628.md) | 45.3% |
 | 637 | [Average of Levels in Binary Tree](/easy/637.md) | 55.8% |
+| 645 | [Set Mismatch](/easy/645.md) | 40.3% |
 | 653 | [Two Sum IV - Input is a BST](/easy/653.md) | 51.1% |
 | 657 | [Judge Route Circle](/easy/657.md) | 69.7% |
 | 661 | [Image Smoother](/easy/661.md) | 47.4% |

easy/100.md

@@ -1,10 +1,12 @@
-# Description
+# 100. Same Tree
+
+## Description
 
 Given two binary trees, write a function to check if they are equal or not.
 
 Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
 
-## Solution
+### Solution
 Solution 1
 ```javascript
 /**
@@ -21,6 +23,7 @@ Solution 1
  * @return {boolean}
  */
 var isSameTree = function(p, q) {
+    "use strict";
     let result = true;
     function dfs(node1, node2) {
         if (node1 && node2) {
@@ -54,6 +57,7 @@ Solution 2
  * @return {boolean}
  */
 var isSameTree = function(p, q) {
+    "use strict";
     if (p && q) {
         let stackP = [p], stackQ = [q];
         let pPtr = null, qPtr = null;
@@ -95,6 +99,7 @@ Solution 3
  * @return {boolean}
  */
 var isSameTree = function(p, q) {
+    "use strict";
     if (p && q) {
         let queue1 = [p], queue2 = [q];
         while (queue1.length && queue2.length) {

easy/104.md

@@ -1,10 +1,12 @@
-# Description
+# 104. Maximum Depth of Binary Tree
+
+## Description
 
 Given a binary tree, find its maximum depth.
 
 The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
 
-## Solution
+### Solution
 Solution 1
 ```javascript
 /**
@@ -20,6 +22,7 @@ Solution 1
  * @return {number}
  */
 var maxDepth = function(root) {
+    "use strict";
     let result = 0;
     let queue = root ? [root] : [];
     while(queue.length) {
@@ -53,6 +56,7 @@ Solution 2
  * @return {number}
  */
 var maxDepth = function(root) {
+    "use strict";
     function dfs(node, depth) {
         if (!node) {
             return depth-1;

easy/107.md

@@ -0,0 +1,65 @@
+# 107. Binary Tree Level Order Traversal II
+
+## Description
+
+Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).
+
+For example:
+Given binary tree `[3,9,20,null,null,15,7]`,
+```
+    3
+   / \
+  9  20
+    /  \
+   15   7
+```
+return its bottom-up level order traversal as:
+```
+[
+  [15,7],
+  [9,20],
+  [3]
+]
+```
+
+### Solution
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * Traverse the binary tree with Breadth-First Search (BFS) algorithm
+ * @param {TreeNode} root
+ * @return {number[][]}
+ */
+var levelOrderBottom = function(root) {
+    "use strict";
+    if (!root) {
+        return [];
+    }
+    let result = [[root.val]];
+    let queue = [root];
+    while (queue.length) {
+        let level = [];
+        let len = queue.length;
+        for (let i = 0; i < len; i++) {
+            let left = queue[i].left, right = queue[i].right;
+            if (left) {
+                queue.push(left);
+                level.push(left.val);
+            }
+            if (right) {
+                queue.push(right);
+                level.push(right.val);
+            }
+        }
+        level.length && result.push(level);
+        queue = queue.slice(len);
+    }
+    return result.reverse();
+};
+```

easy/108.md

@@ -1,8 +1,10 @@
-# Description
+# 108. Convert Sorted Array to Binary Search Tree
+
+## Description
 
 Given an array where elements are sorted in ascending order, convert it to a height balanced BST.
 
-## Solution
+### Solution
 ```javascript
 /**
  * Definition for a binary tree node.

easy/121.md

@@ -1,4 +1,6 @@
-# Description
+# 121. Best Time to Buy and Sell Stock
+
+## Description
 
 Say you have an array for which the *i*<sup>th</sup> element is the price of a given stock on day *i*.
 
@@ -18,13 +20,14 @@ Output: 0
 
 In this case, no transaction is done, i.e. max profit = 0.
 ```
-## Solution
+### Solution
 ```javascript
 /**
  * @param {number[]} prices
  * @return {number}
  */
 var maxProfit = function(prices) {
+    "use strict";
     let profit = 0
     let min = prices[0], max = prices[0];
     for (let i = 1; i < prices.length; i++) {

easy/122.md

@@ -1,19 +1,20 @@
-# Description
+# 122. Best Time to Buy and Sell Stock II
+
+## Description
 
 Say you have an array for which the *i*<sup>th</sup> element is the price of a given stock on day *i*.
 
 Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy one and sell one share of the stock multiple times). However, you may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).
 
-
-
-## Solution
+### Solution
 ```javascript
 /**
  * Solved with two pointers
  * @param {number[]} prices
  * @return {number}
  */
 var maxProfit = function(prices) {
+    "use strict";
     let profit = 0;
     // Use pointer j to find ascending sequences and another pointer i for pointing the current lowest price
     for (let i = 0, j = 0; j < prices.length; j++) {

easy/13.md

@@ -1,17 +1,20 @@
-# Description
+# 13. Roman to Integer
+
+## Description
 
 Given a roman numeral, convert it to an integer.
 
 Input is guaranteed to be within the range from 1 to 3999.
 
-## Solution
+### Solution
 ```javascript
 /**
  * Solved with hash table
  * @param {string} s
  * @return {number}
  */
 var romanToInt = function(s) {
+    "use strict";
     let table = {
         "IV": 4,
         "IX": 9,