HDU 1576 A/B（扩展欧几里德变形）

标签：扩展欧几里德   exgcd   hdu   扩展   gcd   

题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1576

2
1000 53
87 123456789

7922
6060

PS:
n = A%9973, 设A / 9973 = y;

A / B = x    --->>>>    A = B * x;

那么就有： B*x - 9973 * y =  n;

代码如下：

#include <cstdio>
#include <cstring>
#include <cmath>
typedef __int64 LL;

LL exgcd(LL a,LL b,LL &x,LL &y)
{
    if(b == 0)
    {
        x = 1;
        y = 0;
        return a;
    }
    LL r = exgcd(b,a%b,x,y);
    LL t = x;
    x = y;
    y = t-a/b*y;
    return r;
}

LL cal(LL a, LL b, LL c)
{
    LL x, y;
    LL tt = exgcd(a, b, x, y);
    if(c%tt)
        return -1;
    x *= c/tt;
    b/=tt;
    if(b < 0)
        b = -b;
    LL ans = x%b;
    if(ans < 0)
        ans += b;
    return ans;
}
int main()
{
    LL n, b;
    LL t;
    scanf("%I64d",&t);
    while(t--)
    {
        scanf("%I64d%I64d",&n,&b);
        LL ans = cal(b,9973,n);
        if(ans == -1)
            printf("Impossible\n");
        else
            printf("%I64d\n",ans);
    }
    return 0;
}

HDU 1576 A/B（扩展欧几里德变形）

标签：扩展欧几里德   exgcd   hdu   扩展   gcd   

原文地址：http://blog.csdn.net/u012860063/article/details/39801219