SwiftChallenge1v3

import Cocoa

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

func lpf(integer: Int, minGuess: Int = 2) -> Int {
    if let spf = smallestPrimeFactorOf(integer, withMinGuess: minGuess) {
        return lpf(integer/spf, minGuess: spf)
    }
    return integer
}

print(lpf(600851475143))