【LeetCode热题100】【二叉树】验证二叉搜索树

class Solution {
public:
    bool assist(TreeNode *root, long long low, long long high) {
        if (root == nullptr)
            return true;
        if (root->val <= low || root->val >= high)
            return false;
        return assist(root->left, low, root->val) && assist(root->right, root->val, high);
    }

    bool isValidBST(TreeNode *root) {
        return assist(root, LONG_LONG_MIN, LONG_LONG_MAX);
    }
};