AC日记——Success Rate codeforces 807c

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

#define ll long long

inline void in(ll &now)
{
    char Cget=getchar();now=0;
    while(Cget>‘9‘||Cget<‘0‘) Cget=getchar();
    while(Cget>=‘0‘&&Cget<=‘9‘)
    {
        now=now*10+Cget-‘0‘;
        Cget=getchar();
    }
}

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

int main()
{
    ll t,x,y,p,q;
    in(t);
    for(;t--;)
    {
        in(x),in(y),in(p),in(q);
        p/=gcd(p,q),q/=gcd(p,q);
        if(q==p)
        {
            if(x!=y)
            {
                printf("-1\n");
                continue;
            }
        }
        if(p==0)
        {
            if(x!=0)
            {
                printf("-1\n");
                continue;
            }
        }
        ll pos=(q-y%q)%q;
        double ki=(double)p/(double)q,li,ri;
        ll l=0,r=1000000000,ans;
        while(l<=r)
        {
            int mid=l+r>>1;
            li=(double)x/(double)(y+pos+(mid*q));
            ri=(double)(x+pos+mid*q)/(double)(y+pos+mid*q);
            if(ki>=li&&ki<=ri) ans=mid,r=mid-1;
            else l=mid+1;
        }
        printf("%lld\n",pos+ans*q);
//        cout<<pos+ans*q;
//        putchar(‘\n‘);
    }
    return 0;
}