LeetCode-Symmetric Tree

题目链接：https://oj.leetcode.com/problems/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 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.
confused what

"{1,#,2,3}"

means? >
read more on how binary tree is serialized on OJ.
解题思路：此题，采用构建另一个指针，指着根节点root，一个从左搜索，一个从右搜索，比较两棵树是否相同。

/**
* Definition for binary tree
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
bool isSymmetric(TreeNode *root) {
TreeNode *root1 = root;
return isSameTree(root,root1);
}
bool isSameTree(TreeNode *p, TreeNode *q) {
if (p == NULL && q == NULL)
return true;
else if(p == NULL || q == NULL)
return false;
bool valSignal = (p->val == q->val) ? true : false;
bool leftSignal =  isSameTree(p->left,q->right);
bool rightSignal = isSameTree(p->right,q->left);
return (valSignal&leftSignal&rightSignal);
}
};

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