19.3.2 [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 [1,2,2,3,4,4,3] is symmetric:

    1
   / 
  2   2
 /  / 
3  4 4  3

 

But the following [1,2,2,null,3,null,3] is not:

    1
   / 
  2   2
      
   3    3

 

Note:
Bonus points if you could solve it both recursively and iteratively.

class Solution {
public:
    bool thesame(TreeNode*l,TreeNode*r){
        if(l==NULL&&r==NULL)return true;
        else if(l==NULL||r==NULL)return false;
        bool same=true;
        same&=(l->val==r->val);
        if(!same)return false;
        same&=thesame(l->left,r->right);
        if(!same)return false;
        same&=thesame(l->right,r->left);
        return same;
    }
    bool isSymmetric(TreeNode* root) {
        if(root==NULL)return true;
        return thesame(root->left,root->right);
    }
};