[pull] master from youngyangyang04:master

problems/0098.验证二叉搜索树.md

@@ -595,6 +595,43 @@ var isValidBST = function (root) {
 };
 ```
 
+> 迭代法:
+
+```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) {
+	const queue = [];
+	let cur = root;
+	let pre = null;
+	while (cur !== null || queue.length !== 0) {
+		if (cur !== null) {
+			queue.push(cur);
+			cur = cur.left;
+		} else {
+			cur = queue.pop();
+			if (pre !== null && cur.val <= pre.val) {
+				return false;
+			}
+			pre = cur;
+			cur = cur.right;
+		}
+	}
+	return true;
+};
+```
+
 ### TypeScript
 
 > 辅助数组解决：
@@ -637,6 +674,30 @@ function isValidBST(root: TreeNode | null): boolean {
 };
 ```
 
+> 迭代法:
+
+```TypeScript
+function isValidBST(root: TreeNode | null): boolean {
+	const queue: TreeNode[] = [];
+	let cur: TreeNode | null = root;
+	let pre: TreeNode | null = null;
+	while (cur !== null || queue.length !== 0) {
+		if (cur !== null) {
+			queue.push(cur);
+			cur = cur.left;
+		} else {
+			cur = queue.pop()!;
+			if (pre !== null && cur!.val <= pre.val) {
+				return false;
+			}
+			pre = cur;
+			cur = cur!.right;
+		}
+	}
+	return true;
+}
+```
+
 ### Scala
 
 辅助数组解决: