Adding solution of Leetcode problem number 98

leetcode/98.Validate_Binary_Search_Tree.cpp

@@ -0,0 +1,24 @@
+/**
+ * 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 {
+public:
+    bool isValidBST(TreeNode* root) {
+        return check(root,LONG_MIN,LONG_MAX);
+    }
+    bool check(TreeNode* root,long min,long max)
+    {
+        if(!root) return true;
+        if(root && root->val<=min) return false;
+        if(root && root->val>=max) return false;
+        return (check(root->left,min,root->val) && check(root->right,root->val,max) );
+    }
+};