zoj 3609 Modular Inverse 求最小逆元 裸的的扩展欧几里得

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=3609

#include 
#include 
#include 
#include 
using namespace std;

typedef long long LL;

LL e_gcd(LL a, LL b, LL &x, LL &y)
{
    if(b==0){
        x = 1;
        y = 0;
        return a;
    }
    LL ans = e_gcd(b,a%b,x,y);
    LL temp = x;
    x = y;
    y = temp-a/b*y;
    return ans;
}
LL cal(LL a, LL b, LL c)
{
    LL x, y;
    LL gcd = e_gcd(a,b,x,y);
    if(c%gcd!=0) return -1;
    x*=c/gcd;
    b/=gcd;
    if(b<0) b=-b;
    LL ans = x%b;
    if(ans<=0) ans+=b;
    return ans;
}
int main()
{
    int t;
    scanf("%d", &t);
    LL a,b;
    while(t--){
        scanf("%lld %lld", &a, &b);
        LL ans = cal(a,b,1);
        if(ans==-1) printf("Not Exist\n");
        else printf("%lld\n", ans);
    }
    return 0;
}