POJ1006Biorhythms——中国剩余定理

#include<iostream>
#include<cstdio>
using namespace std;
int r[5],st,a[5],s,x,y,t;//r为余数，a为除数
int exgcd(int a,int b,int &x,int &y)
{
	if(b==0)
	{
		x=1;y=0;
		return a;//最大公因数 
	}
	int gcd=exgcd(b,a%b,x,y);
	int t=x;
	x=y;
	y=t-a/b*y;
	return gcd;
}
int main()
{
	a[1]=23;a[2]=28;a[3]=33;
	int n=23*28*33;
	while(1)
	{
		x=0;y=0;s=0;
		for(int i=1;i<=3;i++)
			scanf("%d",&r[i]);
		scanf("%d",&st);
		if(r[1]==-1&&r[2]==-1&&r[3]==-1&&st==-1)return 0;
		for(int i=1;i<=3;i++)
		{
			int m=n/a[i];
			exgcd(m,a[i],x,y);//x为逆元 
			s=(s+x*m*r[i])%n;
			printf("x=%d s=%d\n",x,s);
		}
		s-=st;
		if(s<0||s==0)s+=n;
		t++;
		printf("Case %d: the next triple peak occurs in %d days.\n",t,s);
	}
	return 0;
}