SwiftChallenge1v2

#!/usr/bin/env xcrun swift

import Cocoa

func smallestPrimeFactorOf(integer: Int, andMinGuess minGuess: Int = 2) -> Int? {
    let upperBound = Int(sqrt(Double(integer)))
    
    var attempt = minGuess
    while attempt <= upperBound {
        if integer % attempt == 0 {
            return attempt
        }
        attempt++
    }
    return nil
}

func largestPrimeFactorOf(var integer: Int) -> Int? {
    var largestPrimeFactor: Int?
    
    var smallestPrimeFactor = smallestPrimeFactorOf(integer)
    
    if smallestPrimeFactor == nil {
        return nil
    }
    
    var attempt = integer
    
    while (smallestPrimeFactor != nil) {
        attempt /= smallestPrimeFactor!
        smallestPrimeFactor = smallestPrimeFactorOf(attempt, withMinGuess: smallestPrimeFactor!)
    }
    return attempt
}

print(largestPrimeFactorOf(600851475143))