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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
判断二叉树是否左右对称
/**
* 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==NULL)return true;
queue<TreeNode*> l; //左子树
queue<TreeNode*> r; //右子树
if(root->left==NULL&&root->right==NULL)
return true;
else if(root->left!=NULL&&root->right!=NULL)
{
l.push(root->left);
r.push(root->right);
}
else
return false;
while(!l.empty()&&!r.empty())
{
TreeNode* temp1=l.front();
TreeNode* temp2=r.front();
if(temp1->val!=temp2->val)
return false;
l.pop();
r.pop();
if(temp1->left&&temp2->right)
{
l.push(temp1->left);
r.push(temp2->right);
}
else if((temp1->left==NULL^temp2->right==NULL)==1)
return false;
if(temp1->right&&temp2->left)
{
l.push(temp1->right);
r.push(temp2->left);
}
else if((temp1->right==NULL^temp2->left==NULL)==1)
return false;
}
if(l.empty()&&r.empty())
return true;
else
return false;
}
};leetcode No101. Symmetric Tree
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原文地址：http://blog.csdn.net/u011391629/article/details/52247811
