Prime factors Kata

PrimeFactors.swift

//: Playground - noun: a place where people can play

import UIKit

func primeFactors(of int: Int) -> [Int] {
  var n = int
  var factors: [Int] = []
  var divisor = 2
  while n > 1 {
    while n % divisor == 0 {
      factors.append(divisor)
      n /= divisor
    }
    divisor += 1
  }
  return factors
}

func assertEquals(_ input: [Int], _ expected: [Int]) -> (Bool, String?) {
  let result = input == expected
  var message: String?
  if !result {
    message = "Expected \(expected), got \(input) instead"
  }
  return (result, message)
}

assertEquals(primeFactors(of: 1), [])
assertEquals(primeFactors(of: 2), [2])
assertEquals(primeFactors(of: 3), [3])
assertEquals(primeFactors(of: 4), [2, 2])
assertEquals(primeFactors(of: 5), [5])
assertEquals(primeFactors(of: 6), [2, 3])
assertEquals(primeFactors(of: 7), [7])
assertEquals(primeFactors(of: 8), [2, 2, 2])
assertEquals(primeFactors(of: 9), [3, 3])