From 92b6e2833ee2334d860bf7b2b94f9eb116c94178 Mon Sep 17 00:00:00 2001
From: Buduf <baldaufmarci@gmail.com>
Date: Thu, 14 Apr 2022 13:36:11 +0200
Subject: [PATCH] problem 98

---
 ValidateBinarySearchTree.cpp | 44 ++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 ValidateBinarySearchTree.cpp

diff --git a/ValidateBinarySearchTree.cpp b/ValidateBinarySearchTree.cpp
new file mode 100644
index 0000000..3b919bf
--- /dev/null
+++ b/ValidateBinarySearchTree.cpp
@@ -0,0 +1,44 @@
+#include <bits/stdc++.h>
+
+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 {
+public:
+    bool isValidBST(TreeNode* root) {
+        if (root != nullptr) {
+            return valid(root, INT_MIN, INT_MAX, false, false);
+        }
+        else {
+            return true;
+        }
+    }
+    bool valid(TreeNode* t, int min, int max, bool wasMin, bool wasMax) {
+        if ((wasMin && t->val <= min) || (wasMax && t->val >= max)) {
+            return false;
+        }
+        if (t->left != nullptr) {
+            bool l = valid(t->left, min, t->val, wasMin, true);
+            if (t->right != nullptr) {
+                return l && valid(t->right, t->val, max, true, wasMax);
+            }
+            else {
+                return l;
+            }
+        }
+        else {
+            if (t->right != nullptr) {
+                return valid(t->right, t->val, max, true, wasMax);
+            }
+            else {
+                return true;
+            }
+        }
+    }
+};