hdu 1576 A/B

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

　　简单exgcd应用。。。无压力1y。。。。

/*
 * Author: SCAU_Lyon
 * Problem: hdu 1576
 * Method: ex-gcd
 */

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <cassert>

using namespace std;
typedef __int64 ll;
const int mod = 9973;

void exgcd(int a, int b, ll &x, ll &y, int &d){
    if (b){
        exgcd(b, a % b, y, x, d);
        y -= (a / b) *x;
    }
    else{
        d = a;
        x = 1;
        y = 0;
    }
}

int main(){
    int n, b, d;
    int T;
    ll x, y;

    scanf("%d", &T);
    while (T-- && scanf("%d%d", &n, &b)){
        exgcd(b, mod, x, y, d);
        assert(d == 1);
        x *= n;
        x %= mod;
        while (x < 0) x += mod;
        printf("%I64d\n", x);
    }

    return 0;
}

——written by Lyon