609C - Load Balancing - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
#define size(container) static_cast<int>(container.size())
#define int long long
signed main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n;
  cin >> n;
  vector<int> A(n);
  for(int i=0; i<n; i++) cin >> A[i];

  sort(begin(A), end(A));
  int sum = accumulate(begin(A), end(A), 0ll);

  vector<int> b(n);
  for(int i=0; i<n; ++i){
    b[i] = sum / n;
    if(i < sum % n)
      b[i]++;
  }

  reverse(begin(b), end(b));

  int ans=0;
  for(int i=0; i<n; ++i)
    ans += abs(A[i] - b[i]);
  cout << ans / 2 << endl;
  return 0;
}