uva 11971

#include<bits/stdc++.h>

using namespace std;
typedef long long ull;

ull gcd(ull a,ull b){
    if(b == 0)
        return a;
    return gcd(b,a%b);
}
int main(){
    ull t,n,k,cnt = 0,temp,a,b,c;
    cin >> t;
    while(t--){
        cnt++;
        cin >> n >> k;
 //       scanf("%ulld %ulld",&n,&k);
        a = k+1;
        b = ((long long)1<<k);//这里 1 很重要

        //cout << k << " " << b << endl;
        temp = gcd(b,a);
        a = a/temp;
        b = b/temp;
        c = b - a;
        printf("Case #%d: ",cnt);
        cout << c << "/" << b << endl;
    }
    return 0;
}

原文地址：https://www.cnblogs.com/zhibin123/p/10882788.html