1684D - Traps - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
#define maxn 1000005
#define int long long
int n,t,s,res,b[maxn],dp[maxn],k,a[maxn],ans;
main()
{
    cin>>t;
    while(t--)
    {
        cin>>n>>k;
    ans=0;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        ans += a[i];
        a[i] += i + 1;
    }
    sort(a,a+n,greater<int>());
    for (int i = 0; i < k; i++) ans -= a[i];
    for (int i = 0; i < k; i++) {
        ans += n;
        ans -= i;
    }
    cout<<ans<<endl;
}
}