PAT (Advanced Level) 1096. Consecutive Factors (20)

#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<algorithm>
using namespace std;

long long n;

bool prime(long long x)
{
    if(x==1) return 0;
    if(x==2) return 1;
    for(long long i=2; i*i<=x; i++)
    {
        if(x%i==0) return 0;
    }
    return 1;
}

int main()
{
    scanf("%lld",&n);
    int f=0;

    if(prime(n))
    {
        printf("1\n");
        printf("%lld\n",n);
    }
    else
    {
        for(int len=10; len>=1; len--)
        {
            long long num=1;
            for(long long i=2;; i++)
            {
                if(i==2)
                {
                    for(long long j=i; j<=i+(long long)len-1; j++)
                    {
                        num=num*j;
                        if(num>n) break;
                    }
                }
                else num=num/(i-1)*(i+len-1);

                if(num>n) break;
                if(n%num==0)
                {
                    f=1;
                    printf("%d\n",len);
                    for(long long j=i; j<=i+len-1; j++)
                    {
                        printf("%lld",j);
                        if(j<i+len-1) printf("*");
                    }
                    printf("\n");
                    break;
                }
            }
            if(f==1) break;
        }
    }
    return 0;
}