leetcode solution

didi0613 · didi0613 · commit 187882d956fa · 2016-09-02T12:42:48.000-07:00
diff --git a/validate-binary-search-tree.js b/validate-binary-search-tree.js
@@ -0,0 +1,45 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {boolean}
+ */
+var isValidBST = function (root) {
+    if (root === null) {
+        return true;
+    }
+
+    // inorder sort
+    var ret = [];
+    var stack = [root];
+    var cur = root;
+
+    while (stack.length > 0) {
+        if (cur && cur.left) {
+            cur = cur.left;
+            stack.push(cur);
+        } else {
+            if (stack.length > 0) {
+                var temp = stack.pop();
+                ret.push(temp.val);
+                cur = temp.right;
+                if (cur) {
+                    stack.push(cur);
+                }
+            }
+        }
+    }
+
+    // check whether the result is in order sequence
+    for (var i = 0; i < ret.length; i++) {
+        if (i > 0 && ret[i] <= ret[i - 1]) {
+            return false;
+        }
+    }
+    return true;
+};
