Merge pull request #424 from kok-s0s/master

提供二叉树部分的JavaScript版本

problems/0098.验证二叉搜索树.md

@@ -377,6 +377,75 @@ func isBST(root *TreeNode, min, max int) bool {
 }
 ```
 
+JavaScript版本
+
+> 辅助数组解决
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {boolean}
+ */
+var isValidBST = function (root) {
+    let arr = [];
+    const buildArr = (root) => {
+        if (root) {
+            buildArr(root.left);
+            arr.push(root.val);
+            buildArr(root.right);
+        }
+    }
+    buildArr(root);
+    for (let i = 1; i < arr.length; ++i) {
+        if (arr[i] <= arr[i - 1])
+            return false;
+    }
+    return true;
+};
+```
+
+> 递归中解决
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {boolean}
+ */
+let pre = null;
+var isValidBST = function (root) {
+    let pre = null;
+    const inOrder = (root) => {
+        if (root === null)
+            return true;
+        let left = inOrder(root.left);
+
+        if (pre !== null && pre.val >= root.val)
+            return false;
+        pre = root;
+
+        let right = inOrder(root.right);
+        return left && right;
+    }
+    return inOrder(root);
+};
+```
+
 
 
 -----------------------

problems/0236.二叉树的最近公共祖先.md

@@ -311,7 +311,34 @@ func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
 }
 ```
 
+JavaScript版本
 
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {TreeNode} p
+ * @param {TreeNode} q
+ * @return {TreeNode}
+ */
+var lowestCommonAncestor = function(root, p, q) {
+    if(root === p || root === q || root === null)
+        return root;
+    let left = lowestCommonAncestor(root.left, p , q);
+    let right = lowestCommonAncestor(root.right, p, q);
+    if(left && right)
+        return root;
+    if(!left)
+        return right;
+    return left;
+};
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)

problems/0501.二叉搜索树中的众数.md

@@ -523,6 +523,55 @@ func traversal(root *TreeNode,result *[]int,pre *TreeNode){//遍历统计
 }
 ```
 
+JavaScript版本
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number[]}
+ */
+var findMode = function (root) {
+    let maxCount = 0;
+    let curCount = 0;
+    let pre = null;
+    let res = [];
+    const inOrder = (root) => {
+        if (root === null)
+            return;
+        inOrder(root.left);
+
+        if (pre === null)
+            curCount = 1;
+        else if (pre.val === root.val)
+            curCount++;
+        else
+            curCount = 1;
+        pre = root;
+
+        if (curCount === maxCount)
+            res.push(root.val);
+
+        if (curCount > maxCount) {
+            maxCount = curCount;
+            res.splice(0, res.length);
+            res.push(root.val);
+        }
+
+        inOrder(root.right);
+        return;
+    }
+    inOrder(root);
+    return res;
+};
+```
 
 
 -----------------------

problems/0530.二叉搜索树的最小绝对差.md

@@ -256,6 +256,39 @@ func findMIn(root *TreeNode,res *[]int){
 }
 ```
 
+JavaScript版本
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var getMinimumDifference = function (root) {
+    let arr = [];
+    const buildArr = (root) => {
+        if (root) {
+            buildArr(root.left);
+            arr.push(root.val);
+            buildArr(root.right);
+        }
+    }
+    buildArr(root);
+    let diff = arr[arr.length - 1];
+    for (let i = 1; i < arr.length; ++i) {
+        if (diff > arr[i] - arr[i - 1])
+            diff = arr[i] - arr[i - 1];
+    }
+    return diff;
+};
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)

problems/0617.合并二叉树.md

@@ -370,6 +370,36 @@ func mergeTrees(t1 *TreeNode, t2 *TreeNode) *TreeNode {
 }
 ```
 
+JavaScript:
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root1
+ * @param {TreeNode} root2
+ * @return {TreeNode}
+ */
+var mergeTrees = function (root1, root2) {
+    const preOrder = (root1, root2) => {
+        if (!root1)
+            return root2
+        if (!root2)
+            return root1;
+        root1.val += root2.val;
+        root1.left = preOrder(root1.left, root2.left);
+        root1.right = preOrder(root1.right, root2.right);
+        return root1;
+    }
+    return preOrder(root1, root2);
+};
+```
 
 
 -----------------------

problems/0700.二叉搜索树中的搜索.md

@@ -290,7 +290,64 @@ func searchBST(root *TreeNode, val int) *TreeNode {
 }
 ```
 
+JavaScript版本
 
+> 递归
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {number} val
+ * @return {TreeNode}
+ */
+var searchBST = function (root, val) {
+    if (!root || root.val === val) {
+        return root;
+    }
+    if (root.val > val)
+        return searchBST(root.left, val);
+    if (root.val < val)
+        return searchBST(root.right, val);
+    return null;
+};
+``` 
+
+> 迭代
+
+```javascript
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {number} val
+ * @return {TreeNode}
+ */
+var searchBST = function (root, val) {
+    while (root !== null) {
+        if (root.val > val)
+            root = root.left;
+        else if (root.val < val)
+            root = root.right;
+        else 
+            return root;
+    }
+    return root;
+};
+```