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  • 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 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

    题解:
    数学问题,找规律
    #include<bits/stdc++.h>
    using namespace std;
    const int maxn=100010;
    long double d[maxn];
    int main(){
        int n;
        scanf("%d",&n);
        for(int i=1;i<=n;i++){
            scanf("%Lf",&d[i]);
        }
        long double sum=0,cnt;
        for(int i=1;i<=n;i++){
            cnt=d[i]*i;
            cnt=cnt*(n-i+1);//连乘会导致溢出
            sum=sum+cnt;
        }
        printf("%.2Lf
    ",sum);
        return 0;
    
    }
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  • 原文地址:https://www.cnblogs.com/dreamzj/p/14410293.html
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