c++ prime number function code example

Example 1: c++ find prime numbers

#include 
using namespace std;

int main()
{
  int n, i;
  bool isPrime = true;

  cout << "Enter a positive integer: ";
  cin >> n;

  for(i = 2; i <= n / 2; ++i)
  {
      if(n % i == 0)
      {
          isPrime = false;
          break;
      }
  }
  if (isPrime)
      cout << "This is a prime number";
  else
      cout << "This is not a prime number";

  return 0;
}

Example 2: Write a function to check if a number is prime?

#include 
int main() {
    int n, i, flag = 0;
    printf("Enter a positive integer: ");
    scanf("%d", &n);

    for (i = 2; i <= n / 2; ++i) {

        // condition for non-prime
        if (n % i == 0) {
            flag = 1;
            break;
        }
    }

    if (n == 1) {
        printf("1 is neither prime nor composite.");
    }
    else {
        if (flag == 0)
            printf("%d is a prime number.", n);
        else
            printf("%d is not a prime number.", n);
    }

    return 0;
}

Example 3: c++ prime number program

#include 
using namespace std;

int main() {
    int i, n;
    bool isPrime = true;

    cout << "Enter a positive integer: ";
    cin >> n;

    // 0 and 1 are not prime numbers
    if (n == 0 || n == 1) {
        isPrime = false;
    }
    else {
        for (i = 2; i <= n / 2; ++i) {
            if (n % i == 0) {
                isPrime = false;
                break;
            }
        }
    }
    if (isPrime)
        cout << n << " is a prime number";
    else
        cout << n << " is not a prime number";

    return 0;
}