[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 isSymmetric(TreeNode *root) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if (!root) return true;

return isEqual(root->left, root->right);
}

bool isEqual(TreeNode* n1, TreeNode* n2)
{
if (n1 && n2)
{
if (n1->val == n2->val)
return isEqual(n1->left, n2->right) && isEqual(n1->right, n2->left);
else
return false;
}
else if (!n1 && !n2)
return true;
else
return false;
}

};