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98 Validate Binary Search Tree

Given a binary tree, determine if it is a valid binary search tree (BST).

Assume a BST is defined as follows:

The left subtree of a node contains only nodes with keys less than the node‘s key.
The right subtree of a node contains only nodes with keys greater than the node‘s key.
Both the left and right subtrees must also be binary search trees.
confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.


解题思路：把树中序遍历，然后看是否为递增序列。

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
vector<int> value;
private:
    void traverse(TreeNode *root)
    {
        if(root!=NULL)
        {
            traverse(root->left);
            value.push_back(root->val);
            traverse(root->right);
        }
    }
public:
    bool isValidBST(TreeNode *root) {
        value.clear();
        traverse(root);
        for(int i=1; i<value.size(); i++)
        {
            if(value[i] <= value[i-1])
                return false;
        }
        return true;
    }
};

leetcode_98_Validate Binary Search Tree

标签：c++   leetcode   tree   inorder   

原文地址：http://blog.csdn.net/keyyuanxin/article/details/44197127