#include <climits>//头文件,这里要使用INT_MIN class Solution { public: bool isValidBST(TreeNode* root) { return dfs(root,INT_MIN, INT_MAX); } private: bool dfs(TreeNode* root,int min,int max){ if(!root) return true; if (root->val<=min||root->val>=max) { return false; } return (dfs(root->...