bzoj 3629: [JLOI2014]聪明的燕姿线性筛+dfs

Posted 2021-01-04 lokiii

数论+爆搜
详见这位大佬https://blog.csdn.net/eolv99/article/details/39644419

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int N=100000;
int s,p[N+5],tot,ans[N+5],con;
bool v[N+5];
bool ok(int x)
{
    if(x==1) 
        return 0;
    if(x<=N) 
        return !v[x];
    for(int i=1;p[i]*p[i]<=x;i++)
        if(x%p[i]==0) 
            return 0;
    return 1;
}
void dfs(int la,int nw,int w)
{
    if(w==1)
    {
        ans[++con]=nw; 
        return; 
    }
    if(w-1>p[la]&&ok(w-1))
        ans[++con]=nw*(w-1);
    for(int i=la+1;p[i]*p[i]<=w;i++)
        for(int j=p[i]+1,t=p[i];j<=w;t*=p[i],j+=t)
            if(w%j==0)
                dfs(i,nw*t,w/j);
}
int main()
{
    for(int i=2;i<=N;i++)
    {
        if(!v[i]) 
            p[++tot]=i;
        for(int j=1;i*p[j]<=N;j++)
        {
            v[i*p[j]]=1;
            if(i%p[j]==0) 
                break;
        }
    }
    while(scanf("%d",&s)!=EOF)
    {
        con=0;
        dfs(0,1,s);
        sort(ans+1,ans+con+1);
        printf("%d
",con);
        for(int i=1;i<=con;i++)
            printf("%d%c",ans[i],i==con?‘
‘:‘ ‘);
    }
    return 0;
}