题解 | Forsaken给学生分组

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main() {
    int n, k;
    cin >> n >> k;
    vector<int> v(n);
    for (int i = 0; i < n; i++) cin >> v[i];
    sort(v.begin(), v.end());
    long long sum = 0, now = n;
    for (int i = 0; i < (n + 1) / 2; i++) {
        if (now == k || k == 0) break;
        sum += v[n - i - 1] - v[i];
        now -= 2; k--;
    }
    cout << sum << endl;
}