How to get random element from a set in Swift?

Question

As of Swift 1.2, Apple introduces Set collection type.

Say, I have a set like:

var set = Set(arrayLiteral: 1, 2, 3, 4, 5)
         


        

Answer 1

Probably the best approach is advance which walks successor for you:

func randomElementIndex(s: Set) -> T {
    let n = Int(arc4random_uniform(UInt32(s.count)))
    let i = advance(s.startIndex, n)
    return s[i]
}

(EDIT: Heh; noticed you actually updated the question to include this answer before I added it to my answer... well, still a good idea and I learned something too. :D)

You can also walk the set rather than the indices (this was my first thought, but then I remembered advance).

func randomElement(s: Set) -> T {
    let n = Int(arc4random_uniform(UInt32(s.count)))
    for (i, e) in enumerate(s) {
        if i == n { return e }
    }
    fatalError("The above loop must succeed")
}