Problem-Solving-in-any-Language/ValidateBST.cpp at main · madANGLE0502/Problem-Solving-in-any-Language · GitHub

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// 98.Leetcode {MEDIUM}  [DFS, BST]

#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 isvalidBST(TreeNode *root, long minval, long maxval)
    {

        if (root == NULL)
            return true;
        if (root->val >= maxval || root->val <= minval)
            return false;

        return isvalidBST(root->left, minval, root->val) && isvalidBST(root->right, root->val, maxval);
    }

public:
    bool isValidBST(TreeNode *root)
    {

        return isvalidBST(root, LONG_MIN, LONG_MAX);
    }
};