Question

C++ Recursion

Code a function which displays the first n prime numbers.

The prototype is: void prime (int)

The number of primes to display is passed as the parameter. The function prime itself is not recursive. However, it should call a separate recursive helper function which determines if a given number is prime

#include <iostream>
using namespace std;

void prime(int )

{

}

int main()
{

   prime (21);
  
return 0;
}

Answer 1

SOURCE CODE:

#include <iostream>

using namespace std;
// recursive helper function to determine n is prime or not
bool isprime(int num,int j)
{
    if(num==2)
       return 2;
    if(num< 2)
        return false;
    if(num%j == 0)
        return false;
    if (num<j*j)
        return true;
    return isprime(num,j+1);
}  

void prime(int n)
{
   int i=1;
   for(i=1;i<=n;i++)
   {
       //calling seperate recursive helper function
       if(isprime(i,2)) //if prime printing prime number
       {  
           cout << i << endl;
       }
      
   }
      
}

int main()
{
   //calling prime function
   prime (21);

return 0;
}

CODE SCREENSHOT:

OUTPUT: