Answer to Question #181705 in C++ for Darren

Question

A positive integer n is said to be prime (or, "a prime") if and only if n is greater than 1 and is divisible only by 1 and n. For example, the integers 17 and 29 are prime, but 1 and 38 are not prime. Write a function named "is_prime" that takes a positive integer argument and returns as its value the integer 1 if the argument is prime and returns the integer 0 otherwise. Thus, for example:

cout << is_prime(19) << endl;    // will print 1

cout << is_prime(1) << endl;     // will print 0

cout << is_prime(51) << endl;   // will print 0

cout << is_prime(-13) << endl; // will print 0

Answer 1

#include <iostream>
using std::cout;
using std::endl;


int  is_prime(int n) 
{
    // 1 does not apply to prime numbers
    if (n <=1) 
    {
        return 0;
    }
    for (int i = 2; i < n; i++)
    {
        if (n % i == 0) 
        {
            return 0;
        }
     }
    return 1;
}


int main()
{
    // example of how the function works
    cout << is_prime(19) << endl;    // will print 1
    cout << is_prime(1) << endl;     // will print 0
    cout << is_prime(3) << endl;     // will print 1
    cout << is_prime(51) << endl;   // will print 0
    cout << is_prime(-13) << endl; // will print 0
    return 0;
}