Leetcode 98 Validate Binary Search Tree
Leetcode 98 Validate Binary Search Tree
triplebee
发布于 2018-01-12 14:55:00
发布于 2018-01-12 14:55:00
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.
Example 1:
2
/ \
1 3Binary tree [2,1,3], return true.
Example 2:
1
/ \
2 3Binary tree [1,2,3], return false.
判断二叉搜索树是否合法。
DFS，记录上下界，在每个点判断值是否满足上下界，然后再继续向下访问。
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
bool dfs(TreeNode* root,long long minn,long long maxx)
{
if(!root) return true;
if(root->val<=minn || root->val>=maxx) return false;
if(dfs(root->left,minn,root->val) && dfs(root->right,root->val,maxx)) return true;
return false;
}
bool isValidBST(TreeNode* root) {
return dfs(root,(long long)INT_MIN-1,(long long)INT_MAX+1);
}
};本文参与 腾讯云自媒体分享计划，分享自作者个人站点/博客。
原始发表：2016-10-08 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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