1862E - Kolya and Movie Theatre - CodeForces Solution

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
int main()
{
    ios::sync_with_stdio(false);
    int T;
    cin >> T;
    while (T--)
    {
        int n, m;
        long long res = 0, sum = 0,d;
        cin >> n >> m >> d;
        priority_queue<int, vector<int>, greater<int>> Q;
        for (int i = 1; i <= n; ++i)
        {
            int ai;
            cin >> ai;
            if (ai + sum - d * i > res)
                res = ai + sum - d * i;
            if (ai > 0)
            {
                Q.push(ai);
                sum += ai;
            }
            if (Q.size() == (size_t)m)
            {
                sum -= Q.top();
                Q.pop();
            }
        }
        cout << res << endl;
    }
    return 0;
}