Problem 47 Distinct primes factors （分解因子）

Distinct primes factors

Problem 47

The first two consecutive numbers to have two distinct prime factors are:

14 = 2 × 7
15 = 3 × 5

The first three consecutive numbers to have three distinct prime factors are:

644 = 2² × 7 × 23
645 = 3 × 5 × 43
646 = 2 × 17 × 19.

Find the first four consecutive integers to have four distinct prime factors each. What is the first of these numbers?

代码：

#include<bits/stdc++.h>
using namespace std;
void factor(set<int>& s,  int n)
{
    if(n==1)return;
    int k = (int)sqrt(n);
    int num = 2;
    while( n%num != 0)
    {
        if(num >= k) //最后结束条件 
        {
          s.insert(n); 
          return;
        }
        if(num > 2) num+=2;
        else num++;
    }
    s.insert(num);
    factor(s, n/num);
}

int main()
{
    set<int> s;
    int counter = 0;
    int ans = 0;
    for(int i=1; ;i++)
    {
        factor(s, i);
        if(s.size()== 4)
        { 
            if(ans == 0) ans = i;
            counter++;
        }
        else
        { 
            ans = 0;
            counter = 0;
        }

        if(counter==4)
        {   
            cout<<ans<<endl;
            s.clear();
            break;
        }
        s.clear();
    }
    return 0;

}