Cut tree in two halfs (dfs implementation )

Cut the tree (dfs application)

https://www.hackerrank.com/challenges/cut-the-tree

In  this question , we should cut the tree such that the difference between two halfs would be smallest
as possible .

firstly ,total weight is added as sum. after that:-
It is implemented using recursive dfs. Here each child gives his lower weight to their parents.


#include<bits/stdc++.h>

using namespace std;

int sum=0;
int a[10000000],vis[1000000];
int ans=INT_MAX;
vector<int> v[1000000];


int  dfs(int node)
{
  vis[node]=1;

  int curr=a[node];

 for(int i=0;i<v[node].size();i++)
 {
     if(vis[v[node][i]]==0)
     curr+=dfs(v[node][i]);
 }


 ans=min(ans,abs(sum-curr-curr));
 //cout<<curr<<" "<<ans<<endl;

 return curr;

 vis[node]=0;
}






int main()
{
 int n,i,j,k,l,p,q;
 cin>>n;

 for(i=1;i<=n;i++)
 {
  cin>>a[i];
  sum+=a[i];
 }

  for(i=1;i<n;i++)
  {
   cin>>p>>q;
   v[p].push_back(q);
   v[q].push_back(p);
  }

 int kk=dfs(1);
 cout<<ans<<endl;

return 0;
}