leetcode-101. Symmetric Tree

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

For example, this binary tree is symmetric:



思路：递归，不递归的话用stack，但是逻辑会复杂

/**
* 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 getSymmetric(root->left,root->right);
}

bool getSymmetric(TreeNode* left,TreeNode* right)
{
if(left == NULL || right == NULL)
{
return left == right;
}

if(left->val != right->val)
{
return false;
}

return getSymmetric(left->left,right->right) && getSymmetric(left->right,right->left);
}
};