Question

write a program to print alternate prime numbers till 20

Answer 1

#include<bits/stdc++.h>

using namespace std;

  

/* Function for checking 

number is prime or not */

int prime(int num)

{

    int i, flag = 0;

    for(i = 2; i<= num / 2; i++)

    {

        if(num % i == 0)

        {

            flag = 1;

            break;

        }

    }

      

    // if flag = 0 then number 

    // is prime and return 1

    // otherwise return 0

    if(flag == 0)

        return 1;

    else

        return 0;

}

  

// Function for printing 

// alternate prime number

void print_alternate_prime(int n)

{

    // counter is initialize with 0

    int counter = 0;

  

    // looping through 2 to n-1

    for(int num = 2; num < n; num++)

    {

        // function calling along 

        // with if condition

        if (prime(num) == 1)

        { 

            // if counter is multiple of 2 

            // then only print prime number

            if (counter % 2 == 0)

                cout << num << " ";

                  

            counter ++;

        }

    }

}

  

// Driver code

int main()

{

    int n = 15;

    cout << "Following are the alternate prime"

         << " number smaller than or equal to " 

         << n << endl;

           

    // Function calling 

    print_alternate_prime(n);

}

Hope U Understand!