[leetcode]101. Symmetric Tree

[leetcode]101. Symmetric Tree

Description

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree [1,2,2,3,4,4,3] is symmetric:

1 / \ 2 2 / \ / \3 4 4 3

But the following [1,2,2,null,3,null,3] is not:

1 / \ 2 2 \ \ 3 3

Note: Bonus points if you could solve it both recursively and iteratively.

分析

题目的意思是：判断二叉树是否是对称的。

二叉树基本是递归，不仅要判断对称点的值是否相等，也要判断一个节点存在，对称节点不存在的情况。递归的终止条件为两个节点都为空。

代码

/** * 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 isSymmetric(TreeNode* root) { if(!root){ return true; } return isEqual(root->left,root->right); } bool isEqual(TreeNode* left,TreeNode* right){ if(!left&&!right){ return true; }else if(!left||!right){ return false; } if(left->val!=right->val){ return false; } return isEqual(left->left,right->right)&&isEqual(left->right,right->left); }};

参考文献

​​[编程题]symmetric-tree​​

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。