Charles Wilson's Blog

HackerRank has become a popular showcase for software developers. Its many participants have the ability to choose their language. Recently Apple’s Swift language has been added.

This is all well and wonderful, but as I written about in previous posts, non-UI oriented use of Swift has not been a priority. It’s not impossible, but you have to scrounge for the bits you need to use it.

As those who have used HackerRank know, non-UI is the way of things. So, here are a few bits that make it possible to use Swift in the HackerRank.

Note: In production code, one should always check when unwrapping variables. In HackerRank, input will be well-behaved and the focus is on the internal workings rather than the input mechanism.

Reading a string from the input stream

let string_value = readLine(stripNewline: true)!

Reading a single number from the input stream

let numeric_value = Int(readLine(stripNewline: true)!)!

Reading a string array from the input stream

let stringArray = input.characters
                       .split {$0 == " "}
                       .map (String.init)

Reading a numeric array from the input stream

let numbericArray = input.characters
                         .split {$0 == " "}
                         .map (String.init)
                         .map {(var s) -> Int in return Int(s)!}

Reading mixed values from the input stream

let stringArray = input.characters
                       .split {$0 == " "}
                       .map (String.init)

let iValue1 = Int(stringArray[0])!
let sValue  = stringArray[1]
let iValue2 = Int(stringArray[2])!

Writing single values to the output stream

print(foo)

Writing values in string to the output stream

print ("There are \(found) or \(expected) things")

Writing array values to the output stream

print (array.map { String($0) }.joinWithSeparator(" "))

Why not use extensions, you may ask. You can do that if you like. I thought it would be better here to show the minimal elements. And generally HackerRank in very limited in its input and output aspects.

This should cover all the usual cases for input and output to enable you to use Swift with HackerRank. So, the next time you’re using HackerRank and you don’t see Swift as an option, be sure to ask the author to add it.