validate-binary-serach-tree

Author: jun0811

validate-binary-search-tree/jun0811.js

@@ -0,0 +1,24 @@
+/**
+ * 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}
+ */
+function check(node, min, max) {
+  if (node === null) return true;
+  if ((min !== null && node.val <= min) || (max !== null && node.val >= max)) {
+    return false;
+  }
+
+  return check(node.left, min, node.val) && check(node.right, node.val, max);
+}
+
+function isValidBST(root) {
+  return check(root, null, null);
+}