leetcode98

class Solution {
public:
    vector<int> V;
    void postTree(TreeNode* node) {
        if (node != NULL) {
            if (node->left != NULL) {
                postTree(node->left);
            }
            V.push_back(node->val);
            if (node->right != NULL) {
                postTree(node->right);
            }
        }
    }
    bool isValidBST(TreeNode* root) {
        postTree(root);
        for (int i = 1; i < V.size(); i++) {
            if (V[i] <= V[i - 1]) {
                return false;
            }
        }
        return true;
    }
};

补充一个python的实现：

class Solution:
    def __init__(self):
        self.lists = []
        
    def inOrder(self,root):
        if root != None:
            if root.left != None:
                self.inOrder(root.left)
            self.lists.append(root.val)
            if root.right != None:
                self.inOrder(root.right)
                
    def isValidBST(self, root: 'TreeNode') -> 'bool':
        self.inOrder(root)
        n = len(self.lists)
        for i in range(n-1):
            if self.lists[i] >= self.lists[i+1]:
                return False
        return True