HDU 6624 (2019杭电第五场 1001) fraction (辗转相除求最小分数解 )

#include <bits/stdc++.h>
#define ll long long
using  namespace std;
void gao(ll pa,ll pb,ll qa,ll qb,ll &x,ll &y){
	ll z = (pa+pb-1)/pb;
	if(z<=qa/qb){
		x = z;	y = 1;
		return ;
	}
	pa-=(z-1)*pb;	qa-=(z-1)*qb;
	gao(qb,qa,pb,pa,y,x);
	x+=(z-1)*y;
}
ll p,a,x,y;
int main()
{
	int _;
	for(scanf("%d",&_);_;_--){
		scanf("%lld %lld",&p,&a);
		gao(p,a,p,a-1,x,y);
		ll z = x*a - y*p;
		printf("%lld/%lld\n",z,x);	
	}
	return 0;
}