JavaScript版本的《验证二叉搜索树》

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);
+};
+```
+
 
 
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