# Convert a tree to forest of even nodes in C++

In this tutorial, we will be discussing a program to convert a tree to a forest of even nodes.

For this we will be provided with a binary tree of say N nodes. Our task is to calculate the maximum number of edges that can be removed to get forest of even nodes.

## Example

Live Demo

#include<bits/stdc++.h>
#define N 12
using namespace std;
//returning the number of nodes of subtree
//having the root node
int depth_search(vector<int> tree[N], int visit[N], int *ans, int node){
int num = 0, temp = 0;
//marking nodes as visited
visit[node] = 1;
for (int i = 0; i < tree[node].size(); i++){
if (visit[tree[node][i]] == 0){
//finding total nodes of the sub subtree
temp = depth_search(tree, visit, ans, tree[node][i]);
//if nodes are even, increment the edges to be removed by 1
(temp%2)?(num += temp):((*ans)++);
}
}
return num+1;
}
//returning the maximum number of edges to be removed
int print_maxedge(vector<int> tree[N], int n){
int visit[n+2];
int ans = 0;
memset(visit, 0, sizeof visit);
depth_search(tree, visit, &ans, 1);
return ans;
}
int main(){
int n = 10;
vector<int> tree[n+2];
tree[1].push_back(3);
tree[3].push_back(1);
tree[1].push_back(6);
tree[6].push_back(1);
tree[1].push_back(2);
tree[2].push_back(1);
tree[3].push_back(4);
tree[4].push_back(3);
tree[6].push_back(8);
tree[8].push_back(6);
tree[2].push_back(7);
tree[7].push_back(2);
tree[2].push_back(5);
tree[5].push_back(2);
tree[4].push_back(9);
tree[9].push_back(4);
tree[4].push_back(10);
tree[10].push_back(4);
cout << print_maxedge(tree, n) << endl;
return 0;
}

## Output

2