Answer to Question #241322 in C++ for SCADA HMI

Question

Write an efficient program to determine if a positive integer, N, is prime.
and In terms of N, analyze the worst-case running time of your program?

Answer 1

#include <iostream>

bool is_prime(const int prime){
    if (prime <= 0)
        return false;
    for(int i = 2; i <= prime / 2; i++)
        if(prime % i == 0)
            return false;
    return true;
}

int main() {
    int prime;
    std::cout << "Enter any positive number: ";
    std::cin >> prime;
    if (is_prime(prime))
        std::cout << prime << " is a prime number" << std::endl;
    else
        std::cout << prime << " is not a prime number" << std::endl;
    return 0;
}