validate-binary-search-tree 풀이 추가

junzero741 · junzero741 · commit 8276bc6b5efa · 2026-03-08T19:07:33.000+09:00
diff --git a/validate-binary-search-tree/junzero741.ts b/validate-binary-search-tree/junzero741.ts
@@ -0,0 +1,23 @@
+// TC: O(n)
+// SC: O(n)
+type TreeNode = {
+    val: number
+    left: TreeNode | null
+    right: TreeNode | null
+}
+function isValidBST(root: TreeNode | null): boolean {
+        
+    function dfs(node: TreeNode | null, low: number, high: number): boolean {
+        if(!node) {
+            return true;
+        }
+
+        if(node.val <= low || node.val >= high) {
+            return false;
+        }
+
+        return dfs(node.left, low, node.val) && dfs(node.right, node.val, high)
+    }
+
+    return dfs(root, -Infinity, Infinity);
+};
