#include<iostream>
using namespace std;




/**
 * Definition for a binary tree node.*/
  struct TreeNode {
     int val;
      TreeNode *left;
   TreeNode *right;
      TreeNode() : val(0), left(nullptr), right(nullptr) {}
      TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 };
 
class Solution {
public:
    bool iszero(TreeNode* root)
    {
        if(!root) return true;
        return root->val==0&&iszero(root->left)&&iszero(root->right);
    }
    TreeNode* pruneTree(TreeNode* root) {
        if(!root||iszero(root)) return nullptr;
        if(iszero(root->left)) root->left = nullptr;
        if(iszero(root->right)) root->right =nullptr;
        if(root->left)pruneTree(root->left);
        if(root->right)pruneTree(root->right);
        return root;
    }
};
int mian()
{
    return 0;
}