【扩展欧几里得算法】AcWing878.线性同余方程

AcWing878.线性同余方程

题解

#include <iostream>

using namespace std;

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

int main()
{
    int t, a, b, x, y, m;
    cin >> t;
    while(t -- )
    {
        cin >> a >> b >> m;
        int d = exgcd(a, m, x, y);
        if(b % d == 0) cout << ((long long)b / d * x % m) << endl; 
        else cout << "impossible" << endl;
    }
    return 0;
}