solve(w02): 98. Validate Binary Search Tree

Author: jeongwoo903

validate-binary-search-tree/jeongwoo903.js

@@ -0,0 +1,31 @@
+/*
+* 시간 복잡도: O(n)
+* 공간 복잡도; O(h)
+* -> h는 트리의 높이
+*/
+
+/**
+ * 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}
+ */
+var isValidBST = function(root) {
+  function bst(node , min, max) {
+    if (!node) return true;
+
+    if (node.val <= min || node.val >= max) return false;
+
+    return (
+      bst(node.left, min, node.val) && helper(node.right, node.val, max)
+    );
+  }
+
+  return bst(root, -Infinity, Infinity);
+};