1104 Sum of Number Segments（二刷）

 1 #include<iostream>
 2 using namespace std;
 3 
 4 int main() {
 5     int n;
 6     double t,sum = 0;
 7     cin>>n;
 8     for(int i = 0 ; i < n; ++i) {
 9         cin>>t;
10         sum += (i+1)*t*(n-i);
11     }
12     printf("%.2f\n",sum);
13     return 0;
14 }