luoguP1516 青蛙的约会

Posted 2020-12-28 dream-runner

求 (n-m)*tx+l*ty=y-x，tx最小的解，用exgcd就ok了。

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll exgcd(ll a,ll b,ll &x,ll &y){
    if(b==0){
        x=1;y=0;
        return a;
    }
    ll ret=exgcd(b,a%b,x,y);
    ll temp=x;
    x=y;y=temp-(a/b)*y;
    return ret;
}
int main(){
    ll x,y,n,m,l,ansx,ansy;
    scanf("%lld%lld%lld%lld%lld",&x,&y,&n,&m,&l);
    ll t=exgcd(m-n,l,ansx,ansy);
    ll temp=x-y;l=abs(l/t);
    if(temp%t!=0)printf("Impossible");
    else printf("%lld",(((temp/t)*ansx)%l+l)%l);
    return 0;
}