POJ-1061 青蛙的约会(扩展欧几里德算法)

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <vector>#include <string>#include <cmath>using namespace std;typedef long long LL;void gcd(LL a, LL b, LL &x, LL &y, LL &d){    if(!b){        x = 1;        y = 0;        d = a;    }    else{        LL s1, s2;        gcd(b, a%b, s1, s2, d);        x = s2;        y = s1 - a / b * s2;    }}int main(){//  freopen("in.txt", "r", stdin);    LL x, y, m, n, l;    while(cin >> x >> y >> m >> n >> l){        LL k1, k2, d;        gcd(m-n, -l, k1, k2, d);        if((y-x) % d != 0){            cout << "Impossible" << endl;            continue;        }        else{            k1 *= (y - x) / d;            l /= d;            if(l < 0)             l = -l;            k1 %= l;            if(k1 < 0)             k1 += l;        }        cout << k1 << endl;    }    return 0;}