[Luogu P1495]曹冲养猪

题目链接

中国剩余定理（孙子定理）的裸题。直接放代码。

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
#define ll long long
ll read(){
    ll res=,f=;
    char ch=getchar();
    while(ch<''||ch>''){
        if(ch=='-')f=-;
        ch=getchar();
    }
    while(ch>=''&&ch<=''){
        res=res*+(ch-'');
        ch=getchar();
    }
    return res*f;
}
ll n,a[],b[],ans;
void exgcd(ll a,ll b,ll &x,ll &y){
    if(b==)x=,y=;
    else{
        exgcd(b,a%b,x,y);
        ll xt=x;
        x=y;
        y=xt-a/b*y;
    }
}
void intchina(ll *m,ll *u){
    ll Mk=,M[];
    for(ll i=;i<=n;++i)Mk*=m[i];
    for(ll i=;i<=n;++i){
        M[i]=Mk/m[i];
        ll x,y;
        exgcd(M[i],m[i],x,y);
        ans=(ans%Mk+M[i]*x*u[i]%Mk+Mk)%Mk;
    }
    while(ans<)ans+=Mk;
    ans%=Mk;
}
int main(){
n=read();
for(int i=;i<=n;++i)a[i]=read(),b[i]=read();
intchina(a,b);
cout<<ans;
return ;
}