98.validate-binary-search-tree.cpp

/*
 * @lc app=leetcode id=98 lang=cpp
 *
 * [98] Validate Binary Search Tree
 */

// @lc code=start
/**
 * 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 valid(TreeNode* node, long long min, long long max) {
        if (node == nullptr) return true;
        long long val = node->val;
        return (val < max && val > min) ? (valid(node->left, min, val) &&
                                           valid(node->right, val, max))
                                        : false;
    }

    bool isValidBST(TreeNode* root) {
        return valid(root, LLONG_MIN, LLONG_MAX);
    }
};
// @lc code=end