/**
*knakul853
 **/
class Solution {
public:
    bool isSymmetric(TreeNode* root) {

        if( !root ) return true;

       return  solve(root->left, root->right);

    }

    bool solve(TreeNode* t1, TreeNode* t2)
    {
        if( t1 == t2 ) return true;
        if( !t1 || !t2) return false;

        if(t1->val != t2->val) return false;

        return solve(t1->left, t2->right) && solve(t1->right, t2->left);
    }
};