p2231.cpp

大概POJ上50道比较难的题的代码

#include <iostream>
#include <algorithm>
using namespace std;
const int MAXN = 10001;
long long a[MAXN],s[MAXN];
int main(){
    int n;
    scanf("%d",&n);
    for(int i = 0;i < n;++i) scanf("%lld",&a[i]);
    sort(a,a+n);
    s[0] = a[0];
    for(int i = 1;i < n;++i) s[i] = s[i-1] + a[i];
    long long ans(0);
    for(int i = 0;i < n;++i){
        ans += s[n-1] - 2 * s[i];
        ans -= (n - 2 * i - 2) * a[i];
    }
    cout << ans << endl;
}