Codeforces 808B Average Sleep Time

#include<iostream>#include<vector>#include<string>#include<set>#include<map>#include<algorithm>#include<queue>#include<list>#include<stack>#include<cstdio>#include<fstream>#include<numeric>#include<functional>#include<utility>#include<memory>#include<iomanip>using namespace std;long long int n, k;long long int sum;int main(){while (cin >> n >> k){long long int m;sum = 0;vector<long long int> arr;for (int i = 0; i < n; i++){cin >> m;arr.push_back(m);}vector<long long int> amount(n);int index1 = k - 1;int index2 = n - k;if (index1 <= index2){int start = 0;int t = 1;while (start < index1){amount[start] = t;t++;start++;}int end = n - 1;t = 1;while (end > index2){amount[end] = t;t++;end--;}while (index1 <= index2){amount[index1] = k;index1++;}}else{int start = 0;int t = 1;while (start < index2){amount[start] = t;t++;start++;}t = 1;int end = n - 1;while (end>index1){amount[end] = t;t++;end--;}while (index2 <= index1){amount[index2] = t;index2++;}}for (int i = 0; i < arr.size(); i++){sum += (amount[i] * arr[i]);}double t = n - k + 1;cout << fixed << setprecision(6) << sum / t << endl;}return 0;}