Question

17. Prime Numbers A prime number is a number that is only evenly divisible by itself and 1. For example, the number 5 is prime because it can only be evenly divided by 1 and S. The number 6, how- ever, is not prime because it can be divided evenly by 1, 2, 3, and 6. Write a Boolean function named is_prime which takes an integer as an argument and returns true if the argument is a prime number, or false otherwise. Use the function in a program that prompts the user to enter a number then displays a message indicating whether the number is prime TIP: Recall that the % operator divides one number by another and ret remainder of the division. In an expression such as num1 % num2, the % operator will return 0 if num1 is evenly divisible by num2.

Answer 1

#include <iostream>

using namespace std;

bool is_prime(int n) {
    if(n <= 1) {
        return false;
    } else {
        int i;
        for(i = 2; i < n; ++i) {
            if(n % i == 0) {
                return false;
            }
        }
        return true;
    }
}

int main() {
    int n;
    cout << "Please input a positive integer: ";
    cin >> n;
    if(is_prime(n)) {
        cout << n << " is a prime number." << endl;
    } else {
        cout << n << " is not a prime number." << endl;
    }
    return 0;
}