Problem name: Symmetric trees

Problem statement:

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

Solution:

class Solution {
public:
    bool isMirror(TreeNode* root1, TreeNode* root2){
        if(root1 == NULL && root2 == NULL){
            return true;
        }
        if(root1 && root2 && root1->val == root2->val){
            return isMirror(root1->left, root2->right) && isMirror(root1->right, root2->left);
        }
        return false;
    }
    
    bool isSymmetric(TreeNode* root) {
        return isMirror(root, root);
    }
};