101. Symmetric Tree

题目：

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.
思路：
这道题目，其实很简单，只要稍稍修改我前一篇博客的函数，并调用就好了Same Tree

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 isSameTree(TreeNode* p, TreeNode* q) {
if(p==NULL&&q==NULL)
return true;
else if(p==NULL&&q!=NULL)
return false;
else if(p!=NULL&&q==NULL)
return false;
else
{
if(p->val!=q->val)
return false;
else
return isSameTree(p->left,q->right)&&isSameTree(p->right,q->left);
}

}
bool isSymmetric(TreeNode* root) {
TreeNode* temp = root;
return isSameTree(root,temp);
}
};