hdu 3579 Hello Kiki

不互质的中国剩余定理……

链接http://acm.hdu.edu.cn/showproblem.php?pid=3579

#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<cmath>
#include<iomanip>
using namespace std;
int n,m;
int extend_gcd(int a,int b,int &x,int &y)
{
    int m;
    if(b==0)
    {
        x=1;
        y=0;
        return a;
    }
    else
    {
        m=extend_gcd(b,a%b,x,y);
        int t=x;
        x=y;
        y=t-a/b*y;
    }
    return m;
}
int main()
{
    int t,i,j,a[7],b[7],a1,a2,b1,b2,c,tt,x,y;
    bool flag;
    j=0;
    cin>>t;
    while(t--)
    {
        cin>>n;
        for(i=0;i<n;i++) cin>>a[i];
        for(i=0;i<n;i++) cin>>b[i];
        a1=a[0];b1=b[0];flag=0;
        for(i=1;i<n;i++)
        {
            if(flag) continue;
            a2=a[i];b2=b[i];c=b2-b1;
            int d=extend_gcd(a1,a2,x,y);
            if(c%d)
            {
                flag=true;
                continue;
            }
            tt=a2/d;
            x=(x*c/d%tt+tt)%tt;
            b1=a1*x+b1;
            a1=a1/d*a2;
        }
        if(flag)
        {
            printf("Case %d: -1\n",++j);
            continue;
        }
        else
        {
            if(b1==0&&n>1) b1=a1;
            else if(b1==0&&n==1) b1=a[0];
            printf("Case %d: %d\n",++j,b1);
        }
    }
    return 0;
}