Agustín Covarrubias Agustín Covarrubias - 2 months ago 38
Swift Question

Check if a number is prime?

I'm trying to make an app that checks whether a number is prime or not.

Can someone help me to check the number?

I need a simple answer, not incredibly advanced algorithms. I'm new to programming.

Answer

A simple method is to check all factors up to the square-root of the number. This is NOT the most efficient method, but is sufficient for most numbers you will likely be inputting in an iPhone app. (see https://en.wikipedia.org/wiki/Primality_test for more complex algorithms).

function is_prime(n: int)
    if n <= 1
        return false

    if n <= 3
        return true

    i = 2
    while i*i <= n
        if n % i == 0
           return false
        i = i + 1
    return true