Program to pruning a given binary tree in C++

Suppose we have a binary tree, where every node's value is either a 0 or a 1. We have to find the same tree where every subtree not containing a 1 has been deleted. So if the tree is like −

To solve this, we will follow these steps −

Define a recursive method solve(), this will take the node. the method will be like −
If node is null, then return null
left of node := solve(left of node)
right of node := solve(right of node)
if left of node is null and right of node is also null and node value is 0, then return null
return node

Let us see the following implementation to get better understanding −

Example

Live Demo

#include <bits/stdc++.h>
using namespace std;
class TreeNode{
   public:
   int val;
   TreeNode *left, *right;
   TreeNode(int data){
      val = data;
      left = NULL;
      right = NULL;
   }
};
void inorder(TreeNode *root){
   if(root){
      inorder(root->left);
      cout << root->val << ", ";
      inorder(root->right);
   }
}
class Solution {
   public:
   TreeNode* pruneTree(TreeNode* node) {
      if(!node)return NULL;
      node->left = pruneTree(node->left);
      node->right = pruneTree(node->right);
      if(!node->left && !node->right && !node->val){
         return NULL;
      }
      return node;
   }
};
main(){
   TreeNode *root = new TreeNode(1);
   root->left = new TreeNode(1);
   root->right = new TreeNode(0);
   root->left->left = new TreeNode(1);
   root->left->right = new TreeNode(1);
   root->right->left = new TreeNode(0);
   root->right->right = new TreeNode(1);
   root->left->left->left = new TreeNode(0);
   Solution ob;
   inorder(ob.pruneTree(root));
}

Input

TreeNode *root = new TreeNode(1);
root−>left = new TreeNode(1);
root−>right = new TreeNode(0);
root−>left−>left = new TreeNode(1);
root−>left−>right = new TreeNode(1);
root−>right−>left = new TreeNode(0);
root−>right−>right = new TreeNode(1);
root−>left−>left−>left = new TreeNode(0);