51nod_1417:天堂里的游戏

题目链接： https://www.51nod.com/onlineJudge/questionCode.html#!problemId=1417

假设 ans=n/m,C=(A+B)/2

　　若出正面 E_1 = nA-(m-n)C

　　若出反面 E_2 = (m-n)B-nC

由样例解释可知

得　　m = A+B+2C,n=B+C

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;

LL gcd(LL a,LL b)
{
    return b? gcd(b,a%b):a;
}

int main()
{
    LL T;cin>>T;
    while(T--)
    {
        LL a,b,c;
        cin>>a>>b;
        c=(a+b)/2;
        LL m=a+b+2*c,n=b+c;
        LL g=gcd(m,n);
        printf("%lld/%lld\n",n/g,m/g);
    }
}