Codeforces Round #610 (Div. 2)

B,

题意就是你可以一次购买k件衣服，然后你只需付款最贵的那件价格，问你可以最多买多少件。

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;

int main() {
    int cntTest;
    cin >> cntTest;
    for (int test = 0; test < cntTest; test++) {
        int n, p, k;
        cin >> n >> p >> k;
        int pref = 0;
        int ans = 0;
        vector<int> a(n);
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        sort(a.begin(), a.end());
        for (int i = 0; i <= k; i++) {
            int sum = pref;
            if (sum > p) break;
            int cnt = i;
            for (int j = i + k - 1; j < n; j += k) {
                if (sum + a[j] <= p) {
                    cnt += k;
                    sum += a[j];
                } else {
                    break;
                }
            }
            pref += a[i];
            ans = max(ans, cnt);
        }
        cout << ans << "\n";
    }
}