[ACM] Play the dice-mathematical probability

I haven't completed my questions for more than a year. Today I have made a water question for the competition. I feel the question is bitter and hard to understand.

Then, I read it several times, understood and thought, and achieved results.

There are two writable points:

1: Derivation, composition of the expected ans: First mean + undetermined mean

That is, ANS = (A1 +... An)/n + ans * M/N

Final Result: ANS = (A1 + .. An)/(n-M );

The formula also shows n! = M. The question can also be n = m. It is INF.

2: The accuracy problem. I used to make this mistake, but it was all vague. I paid special attention to it this time.

When judging sum = 0, use int to define sum to judge. AC, use double to judge expected

The most familiar wrong Anser...

The author also explained it in a little bit, providing two connections for everyone to learn. One is Microsoft's official materials.

A blog of step home

Http://technet.microsoft.com/zh-cn/library/system.double

Http://www.jb51.net/article/36935.htm

Do not spray a small white code ~ HA:

#include <stdio.h>int main(){    int n,m;    double ans;    while(scanf("%d",&n)==1)    {        int sum=0;        for(int i=0;i<n;i++)        {            int temp;            scanf("%d",&temp);            sum+=temp;        }        scanf("%d",&m);        for(int i=0;i<m;i++)        {            int temp;            scanf("%d",&temp);        }        if(sum==0)        {            printf("0.00\n");continue;        }        if(n==m)        {            printf("inf\n");continue;        }        ans=(double)sum/(n-m);        printf("%.2lf\n",ans);    }    return 0;}

Record a few URLs that are not carefully viewed:

Http://book.51cto.com/art/201204/326994.htm

Blog.csdn.net/xiaozzhao/article/details/7450042

Http://blog.csdn.net/sgnaw/article/details/12442