leetcode101.SymmetricTree

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

For example, this binary tree is symmetric:

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

But the following is not:

1
/ \
2   2
\   \
3    3

Note:

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

解题思路：判断一棵树是不是一个对称的二叉树，在这里给出了两个思路。一种是递归，一种是进行迭代。

对两颗子树分别进行判断：

代码如下：

/**
* 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;
return isSame(root.left,root.right);

}
bool isSame(TreeNode * left1,TreeNode * right1)
{
if(left1==right1==NULL)
return true;
if(left1==NULL||right1==NULL)
return false;
if(left1->left!=right1->right)
return false;
bool isleft=isSame(left1->left1,right1->right);
bool isright=isSame(left1->right,right1->left);
retrun isleft&&isright;
}
};