Sherlock and his girlfriend CodeForces

    一个数若是合数则必定可以分解为多个质数相乘。有了这个定理分类讨论一下就行了。

#include<bits/stdc++.h>
using namespace std;
int a[100200],n,cnt;
void getprim()
{
    memset(a,0,sizeof(a));
    for(int i=2;i<=n+1;i++)
    {
        if(!a[i])
        {
            for(int j=i+i;j<=n+1;j=j+i)
                a[j]=1;

        }
    }

}
int main()
{
    cin>>n;
    if(n==1)
    {
        cout<<1<<endl<<1<<endl;
    }
    else
        if(n==2)
        {
            cout<<1<<endl<<1<<" "<<1<<endl;
        }
        else
        {
             getprim();
             cout<<2<<endl;
             for(int i=2;i<=n+1;i++)
             {
                 if(!a[i])
                    cout<<1<<" ";
                 else
                    cout<<2<<" ";
             }
             cout<<endl;
        }
    return 0;
}