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How to pass the Fizz Buzz test

Paul Hudson       @twostraws

The Fizz Buzz test is a simple coding test used in some coding interviews. It’s not designed to be hard, in fact quite the opposite – it’s designed to be easy enough that most folks can solve it without feeling too pressured.

To pass the test you must write a function that accepts an integer and returns a string. Which string to return depends on the input number:

  • If the integer is evenly divisible by three, it should return “Fizz”.
  • If the integer is evenly divisible by five, it should return “Buzz”.
  • If the integer is evenly divisible by three and five, it should return “Fizz Buzz”.
  • Otherwise it should return the string form of the input number.

There are lots of ways this can be solved in Swift, but I think one of the most interesting is to use tuples like this:

func fizzbuzz(number: Int) -> String {
    switch (number % 3 == 0, number % 5 == 0) {
    case (true, false):
        return "Fizz"
    case (false, true):
        return "Buzz"
    case (true, true):
        return "FizzBuzz"
    case (false, false):
        return String(number)
    }
}

print(fizzbuzz(number: 15))

This approach breaks down a large input space – any number – into simple combinations of true and false, and we then use tuple pattern matching in the case statements to select the correct output.

Available from iOS 8.0

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