validate binary search tree 문제

Author: ymir0804

validate-binary-search-tree/ymir0804.java

@@ -0,0 +1,15 @@
+class Solution {
+    public boolean isValidBST(TreeNode root) {
+        return isValid(root, Long.MIN_VALUE, Long.MAX_VALUE);
+    }
+    public boolean isValid(TreeNode node, long min, long max) {
+        if (node == null) {
+            return true;
+        }
+        if (node.val <= min || node.val >= max) {
+            return false;
+        }
+        return isValid(node.left, min, node.val) && isValid(node.right, node.val, max);
+    }
+
+}