题目链接 实现 #include <cstdio> #define MAXSIZE 100000 using namespace std; int main() { int N; double temp, all=0; scanf("%d", &N); int i; for (i = 1; i <= N; i++) { scanf("%lf", &temp); all =all+ temp*i*(N+1-i); } printf("%.2f", all); return 0; }