hdoj 5194 DZY Loves Balls

DZY Loves Balls

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 746    Accepted Submission(s): 411

Problem Description

There are n black balls and m white balls in the big box.

Now, DZY starts to randomly pick out the balls one by one. It forms a sequence S. If at the i-th operation, DZY takes out the black ball, Si=1, otherwise Si=0.

DZY wants to know the expected times that '01' occurs in S.

 

Input

The input consists several test cases. (TestCase≤150)

The first line contains two integers, n, m(1≤n,m≤12)

 

Output

For each case, output the corresponding result, the format is p/q(p and q are coprime)

 

Sample Input

1 12 3

 

Sample Output

1/26/5
Hint
Case 1: S='01' or S='10', so the expected times = 1/2 = 1/2Case 2: S='00011' or S='00101' or S='00110' or S='01001' or S='01010' or S='01100' or S='10001' or S='10010' or S='10100' or S='11000',so the expected times = (1+2+1+2+2+1+1+1+1+0)/10 = 12/10 = 6/5
 

 

代码：

#include<stdio.h>#include<string.h>int gcd(int x,int y){int t;while(y){t=y;y=x%y;x=t;}return x;}int main(){int n,m,a;while(~scanf("%d%d",&n,&m)){int x=n*m;int y=n+m;a=gcd(x,y);printf("%d/%d\n",x/a,y/a);}return 0;}