풀이1: Validate Binary Search Tree #251

Author: seungseung88

validate-binary-search-tree/seungseung88.js

@@ -0,0 +1,20 @@
+/**
+ * @param {TreeNode} root
+ * @return {boolean}
+ */
+var isValidBST = function (root) {
+  let prev = -Infinity;
+
+  const inorder = (node) => {
+    if (!node) return true;
+
+    if (!inorder(node.left)) return false;
+
+    if (node.val <= prev) return false;
+    prev = node.val;
+
+    return inorder(node.right);
+  };
+
+  return inorder(root);
+};