【leetcode】Symmetric Tree

/**
* 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 check(TreeNode *lefNode,TreeNode *rigNode)
{
if((lefNode==NULL&&rigNode!=NULL)||(lefNode!=NULL&&rigNode==NULL))
return false;
if(lefNode==NULL&&rigNode==NULL)
return true;
if(lefNode->val!=rigNode->val)
return false;
else
return check(lefNode->left,rigNode->right)&&check(lefNode->right,rigNode->left);
}

bool isSymmetric(TreeNode *root) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if(root==NULL)
return true;
else
return check(root->left,root->right);
}
};