# PAT B1049A1104 题解

1104 Sum of Number Segments （20 分）
Given a sequence of positive numbers, a segment is defined to be a consecutive subsequence. For example, given the sequence { 0.1, 0.2, 0.3, 0.4 }, we have 10 segments: (0.1) (0.1, 0.2) (0.1, 0.2, 0.3) (0.1, 0.2, 0.3, 0.4) (0.2) (0.2, 0.3) (0.2, 0.3, 0.4) (0.3) (0.3, 0.4) and (0.4).

Now given a sequence, you are supposed to find the sum of all the numbers in all the segments. For the previous example, the sum of all the 10 segments is 0.1 + 0.3 + 0.6 + 1.0 + 0.2 + 0.5 + 0.9 + 0.3 + 0.7 + 0.4 = 5.0.

Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N, the size of the sequence which is no more than 10
​5
​​ . The next line contains N positive numbers in the sequence, each no more than 1.0, separated by a space.

Output Specification:
For each test case, print in one line the sum of all the numbers in all the segments, accurate up to 2 decimal places.

Sample Input:
4
0.1 0.2 0.3 0.4
Sample Output:
5.00

``````#includecstdio
#includeiostream
using namespace std;
const int maxn=100010;
double num[maxn];
int main(){
int n;
cinn;
double sum=0;
for(int i=1;i=n;i++){
scanf("%lf",num[i]);
sum+=num[i]*(n+1-i)*i;
}
printf("%.2f",sum);
return 0;
}
``````
• 星秀
• 04:34
• 02:16
• 05:50
• 11:53
• 14:41