整除问题---素数筛法

#include<iostream>
#include<cstdio>
#include<cstring>
#include<vector>
#include<map>
#include<algorithm>
using namespace std;
const int maxn=1000;
int xx[maxn];
int yy[maxn];
vector<int >prime;
bool isPrime[maxn];
void Initial (){
for(int i=0;i<maxn;i++)
isPrime[i]=true;
isPrime[0]=false;
isPrime[1]=false;
for(int i=2;i<maxn;++i)
{
    if(!isPrime[i])
    continue;
    prime.push_back(i);
    for(int j=i*i;j<maxn;j+=i)
    isPrime[j]=false;
}
return ;
}

int main()
{
    Initial();
    int n,m;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        memset(xx,0,sizeof(xx));
         memset(yy,0,sizeof(yy));
        for(int i=2;i<=n;i++)
        {
            for(int j=0;j<prime.size()&&prime[j]<=n;++j)
            {
                int ii=i;
                int factor=prime[j];
                while(ii%factor==0)
                {
                    ii/=factor;
                    xx[factor]++;
                }
            }
        }
        int num=1000000;
        for(int j=0;j<prime.size()&&prime[j]<=n;++j)
            {
                int factor=prime[j];
                while(m%factor==0)
                {
                    m/=factor;
                    yy[factor]++;
                }
            }
            for(int i=0;i<maxn;i++)
            {
                if(yy[i]!=0)
                num=min(num,xx[i]/yy[i]);
                if(num==0)
                break;
            }
            printf("%d\n",num);
    }
    return 0;
}