ValidateBST.cpp

#include<bits/stdc++.h>
using namespace std;
/**
 * 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 isValid(TreeNode* root, long min, long max){
        if(!root){
            return true;
        }
       if(root->val>min && root->val<max){
          return isValid(root->left, min, root->val) && isValid(root->right, root->val, max);
       }
       return false;
        
    }
    bool isValidBST(TreeNode* root) {
       return isValid(root, LONG_MIN, LONG_MAX);
    }
};