More Divisors ZOJ - 2562（反素数）

#include <iostream>
#include <cstdio>

using namespace std;

#define ll unsigned long long
#define INF 0x3f3f3f3f3f3f3f3f

ll n;
ll ans;
ll ans1;
int p[16] = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53};

void dfs(int d,ll t,int num)
{
    if(d>16||t>n) return;
    if(t<=n&&num>=ans)
    {   
        if(num>ans)
        {
            ans=num;
            ans1=t;
        }
        else if(num==ans)
        {
            if(t<ans1)
                ans1=t;
        }
    }
    for(int i=1;i<=64;i++)
    {
        if(t>n)
            break;
        t*=p[d];
        dfs(d+1,t,num*(i+1));
    }
}
int main()
{
    while(scanf("%lld",&n)==1)
    {
        ans=0;
        ans1=INF;
        dfs(0,1,1);
        cout<<ans1<<endl;
    }
}