Question

Thats all in title.
In simple i had write this.

#include <iostream>
using namespace std;  
int main()  
{ 
    int a,i;  
    cout<<"Enter a number: ";  
    cin>>a;  
    for (i=2;i<=a/2;i++)  
    {  
        if (a%i==0)  
        {  
            cout<<"Its not Prime Number.";  
           system ("pause");  
            return 0;  
        }  
    }  
    cout<<"Its a Prime number.";  
    system ("pause");  
    }   

The main thing is WITHOUT using loop and with recursive function.

Answer 1

Here’s a recursive primality test function:

int test_prime(unsigned n, unsigned d)
{
    if (n < 2) {
        return 0;
    }

    if (d == 1) {
        return 1;
    } else {
        if (n % d == 0) {
            return 0;
        } else {
            return test_prime(n, d - 1);
        }
    }
}

Use it like:

unsigned n;
std::cin >> n;
std::cout << (test_prime(n, n / 2) ? "prime" : "not prime") << "\n";