/** * struct TreeNode { * int val; * struct TreeNode *left; * struct TreeNode *right; * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {} * }; */ class Solution { public: /** * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可 * * * @param root TreeNode类 * @return bool布尔型 */ void answer(TreeNode*root,vector <int> &ans) { if(root) { answer(root->left,ans); ans.push_back(root->val); answer(root->right,ans); } } bool isValidBST(TreeNode* root) { vector <int> ans; answer(root,ans); vector <int> a=ans; sort(a.begin(),a.end()); return a==ans; } };