validate-binary-search-tree solution

Author: 이호찬

validate-binary-search-tree/lhc0506.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}
+ */
+var isValidBST = function(root) {
+    const dfs = (node, min, max) => {
+        if (!node) return true;
+        if (!((node.val > min) && (node.val < max))) return false;
+
+        return dfs(node.left, min, node.val) && dfs(node.right, node.val, max);
+    }
+
+    return dfs(root, Number.MIN_SAFE_INTEGER, Number.MAX_SAFE_INTEGER);
+};
+
+// 시간 복잡도 O(n) , 공간 복잡도 최악의 경우 O(n)