Codeforces Round #536 (Div. 2) C. Lunar New Year and Number Division(思维)

#include <bits/stdc++.h>
#define ll long long
using namespace std;
int n;
int pre[300005];

int main()
{
  scanf("%d",&n);
  for(int i=0;i<n;i++){
    scanf("%d",&pre[i]);
  }
  sort(pre, pre + n);
  ll ans = 0;
  for(int i=0,j=n-1;i<n/2;i++,j--){
    ans += ((ll)(pre[i]+pre[j]) * (ll)(pre[i]+pre[j]));
  }
  printf("%lld\n", ans);
  return 0;
}