98. 验证二叉搜索树
/** * 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) { vector<int> v1; stack<TreeNode *>s1; TreeNode *p = root; while(p || !s1.empty()){ if(p){ s1.push(p); p=p->left; }else{ p = s1.top(); s1.pop(); v1.push_back(p->val); p=p->right; } } for(int i=0;i<v1.size()-1;i++){ if(v1[i]>=v1[i+1]){ return false; } } return true; } };