Finish Validate Binary Search Tree

liril-net · liril-net · commit 36de4356428e · 2016-02-18T23:35:27.000+08:00
diff --git a/JavaScript/Tree/Validate-Binary-Search-Tree.js b/JavaScript/Tree/Validate-Binary-Search-Tree.js
@@ -0,0 +1,30 @@
+//
+// Copyright (c) 2016 by liril.net. All Rights Reserved.
+//
+
+/**
+ * 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) {
+  var valid = function(node, min, max) {
+    if (!node) {
+      return true;
+    }
+
+    if (node.val <= min || node.val >= max) {
+      return false;
+    }
+
+    return (valid(node.left, min, node.val) &&
+            valid(node.right, node.val, max));
+  };
+  return valid(root, Number.NEGATIVE_INFINITY, Number.POSITIVE_INFINITY);
+};
diff --git a/README.md b/README.md
@@ -66,9 +66,11 @@ Tree
 │       ├── Populating-Next-Right-Pointers-in-Each-Node-II.js
 │       ├── Populating-Next-Right-Pointers-in-Each-Node.js
 │       ├── Same-Tree.js
-│       └── Symmetric-Tree.js
+│       ├── Symmetric-Tree.js
+│       └── Validate-Binary-Search-Tree.js
 ├── README.md
 └── package.json
 
-6 directories, 48 files
+6 directories, 49 files
+
 ```
