青蛙的约会

扩展欧几里得

简单的经典题目

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#define Mod 1000000007
#define SMod 10007
#define lll __int64
#define ll long long
using namespace std;
#define N 1000007

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

ll gcd(ll a,ll b)
{
    if(!b)
        return a;
    return gcd(b,a%b);
}

int main()
{
    ll x,y,m,n,L;
    ll kx,ky;
    while(scanf("%lld%lld%lld%lld%lld",&x,&y,&m,&n,&L)!=EOF)
    {
        ll nm = n-m;
        ll delta = x-y;
        if(nm < 0)
        {
            nm = m-n;
            delta = y-x;
        }
        ll d = exgcd(nm,L,kx,ky);
        if(delta%d)
        {
            puts("Impossible");
            continue;
        }
        ll t = L/d;
        //printf("%lld
",t);
        printf("%lld
",res);
    }
    return 0;
}