题目链接:
Time Limit: 2000/1000 MS (Java/Others)
Memory Limit: 65536/65536 K (Java/Others)
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <bits/stdc++.h>
#include <stack>
#include <map>
 
using namespace std;
 
#define For(i,j,n) for(int i=j;i<=n;i++)
#define mst(ss,b) memset(ss,b,sizeof(ss));
 
typedef  long long LL;
 
template<class T> void read(T&num) {
    char CH; bool F=false;
    for(CH=getchar();CH<‘0‘||CH>‘9‘;F= CH==‘-‘,CH=getchar());
    for(num=0;CH>=‘0‘&&CH<=‘9‘;num=num*10+CH-‘0‘,CH=getchar());
    F && (num=-num);
}
int stk[70], tp;
template<class T> inline void print(T p) {
    if(!p) { puts("0"); return; }
    while(p) stk[++ tp] = p%10, p/=10;
    while(tp) putchar(stk[tp--] + ‘0‘);
    putchar(‘\n‘);
}
 
const LL mod=1e9+7;
const double PI=acos(-1.0);
const LL inf=1e18;
const int N=3e5+10;
const int maxn=2e3+14;
const double eps=1e-12;
LL gcd(LL a,LL b)
{
    if(b==0)return a;
    return gcd(b,a%b);
}
int main()
{
    LL n,m;
    while(1)
    {
        read(n);read(m);
        if(n==0&&m==0)break;
        if(m==1)printf("0/1\n");
        else 
        {
            LL temp=gcd(n*(m-1),m*m);
            printf("%lld/%lld\n",n*(m-1)/temp,m*m/temp);
        }
    }
    return 0;
}
hdu-5810 Balls and Boxes(概率期望)
原文:http://www.cnblogs.com/zhangchengc919/p/5755050.html