A - Easy Number Game
水。
1 #include <bits/stdc++.h> 2 using namespace std; 3 4 #define ll long long 5 #define N 100010 6 ll arr[N]; 7 int n, m; 8 9 int main() 10 { 11 int t; scanf("%d", &t); 12 while (t--) 13 { 14 scanf("%d%d", &n, &m); 15 for (int i = 1; i <= n; ++i) scanf("%lld", arr + i); 16 sort(arr + 1, arr + 1 + n); 17 ll res = 0; 18 for (int i = 1; i <= m; ++i) 19 res += arr[i] * arr[2 * m - i + 1]; 20 printf("%lld\n", res); 21 } 22 return 0; 23 }