题解

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin >> n;
    int a[n+1];
    for (int i=0;i<n;i++){
        cin >> a[i];
    }
    sort(a,a+n,greater<int>());
    a[n]=0;    
    int sum1=a[0];
    for (int i=3;i<n;i=i+4){
        sum1=sum1+a[i]+a[i+1];
    }
    int sum2=0;
    for (int i=1;i<n;i=i+4){
        sum2=sum2+a[i]+a[i+1];
    }
    int res;
    res=sum1-sum2;
    if (res>=0) cout << res << " ";
    else cout << -res<< " ";

    return 0;
}