ProjectEuler Problem-3 Solution

Problem :

The prime factors of 13195 are 5, 7, 13 and 29.
What is the largest prime factor of the number 600851475143 ?

Solution :

#include<iostream>
using namespace std;
#include<conio.h>
 void checkprime(unsigned long int a)
 {
  int flag=1;
  for(int i=2;i<a;i++)
  if(a%i==0)
  flag=0;
  
  if(flag==0)
  cout<<endl<<a<<" is not a prime number";
  else
  cout<<endl<<a<<" is a prime number";
 }
int main()
{
   unsigned long int num;
   int tmp,j=0;
   int arr[25]; 
 cout<<endl<<"Enter any number :";
 cin>>num;

 while(num!=1)
 { 
    for(int i=2;i<=num;i++)
    {
    if(num%i==0)
    {
     num=num/i;
     arr[j++]=i;
     break;
    }
    }
    }
 for(int i=0;i<j;i++)
 {
 //cout<<" "<<arr[i];
 checkprime(arr[i]);
    }
}