From eb99170858a261a4c3faa33c645655a71538bbc6 Mon Sep 17 00:00:00 2001
From: Youngsang Suh <60172447+youngsangsuh@users.noreply.github.com>
Date: Fri, 26 May 2023 15:11:05 -0700
Subject: [PATCH 1/2] Create solution.cpp

---
 Leetcode/98/ysuh/solution.cpp | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 Leetcode/98/ysuh/solution.cpp

diff --git a/Leetcode/98/ysuh/solution.cpp b/Leetcode/98/ysuh/solution.cpp
new file mode 100644
index 0000000..9622cc2
--- /dev/null
+++ b/Leetcode/98/ysuh/solution.cpp
@@ -0,0 +1,29 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+private:
+    long int left_max_ = LONG_MAX;
+    long int right_min_ = LONG_MIN;
+    bool treeWalker(TreeNode* parent, long int left_max, long int right_min) {
+        if(parent == NULL) return true;
+        if(parent->val >= left_max || parent->val <= right_min){
+            return false;
+        }
+        return treeWalker(parent->left, parent->val, right_min) && treeWalker(parent->right, left_max ,parent->val);
+    }
+
+public:
+    bool res = true;
+    bool isValidBST(TreeNode* root) {
+        return treeWalker(root, left_max_, right_min_);
+    }
+};

From 9f75518e8139e78bcb947d7d13da1b06fc383640 Mon Sep 17 00:00:00 2001
From: GitHub Action <action@github.com>
Date: Fri, 26 May 2023 22:14:11 +0000
Subject: [PATCH 2/2] Add README.md file

---
 Leetcode/98/ysuh/README.md | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 Leetcode/98/ysuh/README.md

diff --git a/Leetcode/98/ysuh/README.md b/Leetcode/98/ysuh/README.md
new file mode 100644
index 0000000..b82ae73
--- /dev/null
+++ b/Leetcode/98/ysuh/README.md
@@ -0,0 +1,12 @@
+## Link
+[Validate Binary Search Tree](https://leetcode.com/problems/validate-binary-search-tree/)
+
+## Topic
+- Tree
+- Recursion
+
+## Approach
+We shrink the left & right available range while traversing down the tree with recursive call
+
+## Note
+All the leaves at the left should be smaller than the parent and at the right should be greater than the parent.