LeetCode: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:

    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.

/**
 * 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) return true;
        else
            return isSymmetric(root->left,root->right);
        
    }
    
    bool isSymmetric(TreeNode *left,TreeNode *right)
    {
        if(!left&&!right) return true;
        if(!left||!right) return false;
        return left->val==right->val&&isSymmetric(left->left,right->right)&&isSymmetric(left->right,right->left);
    }
};