PAT_A1104#Sum of Number Segments

Source:

PAT A1104 Sum of Number Segments (20 分)

Description:

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 1. 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

Key:

模拟题

Attention:

i*(n-i+1)*x，3和4测试点会报错

Code:

 #include<cstdio>

 int main()

 {

 #ifdef ONLINE_JUDGE

 #else

     freopen("Test.txt", "r", stdin);

 #endif // ONLINE_JUDGE

     int n;

     double x,sum=;

     scanf("%d", &n);

     for(int i=; i<=n; i++)

     {

         scanf("%lf", &x);

         sum += (x*i*(n-i+));

     }

     printf("%.2f\n", sum);

     return ;

 }

巴特西

PAT_A1104#Sum of Number Segments

Source:

Description:

Input Specification:

Output Specification:

Sample Input:

Sample Output:

Key:

Attention:

Code:

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