hdu4762（数学概率）

Cut the Cake

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 885    Accepted Submission(s): 432

Problem Description

MMM got a big big big cake, and invited all her M friends to eat the cake together. Surprisingly one of her friends HZ took some (N) strawberries which MMM likes very much to decorate the cake (of course they also eat strawberries, not just for decoration).
HZ is in charge of the decoration, and he thinks that it‘s not a big deal that he put the strawberries on the cake randomly one by one. After that, MMM would cut the cake into M pieces of sector with equal size and shape (the last one came to the party will
have no cake to eat), and choose one piece first. MMM wants to know the probability that she can get all N strawberries, can you help her? As the cake is so big, all strawberries on it could be treat as points.

Input

First line is the integer T, which means there are T cases.

For each case, two integers M, N indicate the number of her friends and the number of strawberry.

(2 < M, N <= 20, T <= 400)

Output

As the probability could be very small, you should output the probability in the form of a fraction in lowest terms. For each case, output the probability in a single line. Please see the sample for more details.

Sample Input

2
3 3
3 4

Sample Output

1/3
4/27

题意：n颗草莓，把蛋糕分成m块，问选到n颗草莓全在一块蛋糕的概率

思路：公式为n / m^(n-1) ，用大数乘法算出即可

时间： 2024-08-06 11:43:36

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