版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/qq_26398495/article/details/82383641
题目链接
题目分析
给出一段序列,求出所有子序列的数值和!
解题思路:寻找规律
在序列下方用横线画出所有集合,就能很明显看出规律;
第i
个数,出现(N - i + 1)
次,共出现i
组!
AC程序(C++)
/**********************************
*@ID: 3stone
*@ACM: PAT.A1104 Sum of Number Segments
*@Time: 18/8/26
*@IDE: VSCode 2018 + clang++
***********************************/
#include<cstdio>
using namespace std;
const int maxn = 100010;
double number[maxn];
int main() {
int n;
while(scanf("%d", &n) != EOF) {
double sum = 0;
for(int i = 1; i <= n; i++){
scanf("%lf", &number[i]);
}
for(int i = 1; i <= n; i++) {
sum += (number[i] * i * (n - i + 1));
}
printf("%.2f\n", sum);
}//while
return 0;
}