标签：.com lan not bug 今天 更新 win whether round
原题链接：https://leetcode.com/problems/symmetric-tree/
题目如下：
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
目前，我只实现了递归版本，非递归版本稍后更新。
递归版本代码如下：
语言：C++
1 /** 2 * Definition for a binary tree node. 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 bool isSymmetric(TreeNode* root) { 13 if(root == NULL) 14 return true; 15 else 16 return isSymmetric(root->left,root->right); 17 } 18 bool isSymmetric(TreeNode* lefttree,TreeNode* righttree) 19 { 20 if((lefttree == NULL)&&(righttree == NULL)) 21 { 22 return true; 23 } 24 else if((lefttree == NULL)&&(righttree != NULL)) 25 { 26 return false; 27 } 28 else if((lefttree != NULL)&&(righttree == NULL)) 29 { 30 return false; 31 } 32 else if((lefttree != NULL)&&(righttree != NULL)&&(lefttree->val != righttree->val)) 33 { 34 return false; 35 } 36 else 37 { 38 return isSymmetric(lefttree->left,righttree->right) && isSymmetric(lefttree->right,righttree->left); 39 } 40 } 41 };
此代码在最开始提交时，结果总是不对。原因：
将 "lefttreel != righttree" 改为"lefttree->val != righttree->val"，需要比较的不是节点，而是节点的value。
另外，今天get到一句感触颇深的话：不能靠Debug写代码，与各位共勉，谢谢！
标签：.com lan not bug 今天 更新 win whether round
原文地址：http://www.cnblogs.com/jingjingblog/p/6250213.html
