hdu 1576 A/B

原题链接：hdu 1576 A/B

同样是用扩展的欧几里得算法。A = 9973k+n = xB，从而转化为：xB-9973k=n求解x即可。

具体扩展欧几里得算法请参考：hdu 2669 Romantic

代码如下：

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <cstring>
#define     MOD 9973
using namespace std;
typedef long long LL;
void exgcd(LL a, LL b, LL &d, LL &x, LL&y)
{
    if( b == 0 )
    {
        d = a;
        x = 1;
        y = 0;
    }
    else
    {
        exgcd(b, a%b, d, x, y);
        int t = x;
        x = y;
        y = t - (a/b)*y;
    }
}
int main(int argc, char *argv[])
{
    int T;
    scanf ( "%d", &T );
    int n, a, b;
    LL d, x, y;
    while( T-- )
    {
        scanf("%d%d", &n, &b);   
        a = MOD;
        exgcd(a, b, d, x, y);
        y = (y%MOD)*(n/d)%MOD;
        y = (y+MOD)%MOD;
        cout<<y<<endl;
    }
}