1. bool isSymmetrical(TreeNode* pRoot)
    2. {
    3.     return !pRoot || judge(pRoot->left, pRoot->right);
    4. }
    5. bool judge(TreeNode* p1, TreeNode* p2){
    6.     if(!p1 && !p2)return true;
    7.     else if(!p1 || !p2)return false;
    8.     else{
    9.         if(p1->val != p2->val)return false;
    10.         else{
    11.             return judge(p1->left, p2->right) && judge(p1->right, p2->left);
    12.         }
    13.     }
    14. }