Apple Swift - Generate combinations with repetition

Question

I\'m trying to generate a nested array containing all combinations with repetition in Apple\'s Swift programming language.

An detailed explanation of combinations wi

Answer 1

Updated @richgordonuk answer for Swift 4 which provides a non-repetitive combination:

func combinations(source: [T], takenBy : Int) -> [[T]] {
    if(source.count == takenBy) {
        return [source]
    }

    if(source.isEmpty) {
        return []
    }

    if(takenBy == 0) {
        return []
    }

    if(takenBy == 1) {
        return source.map { [$0] }
    }

    var result : [[T]] = []

    let rest = Array(source.suffix(from: 1))
    let subCombos = combinations(source: rest, takenBy: takenBy - 1)
    result += subCombos.map { [source[0]] + $0 }
    result += combinations(source: rest, takenBy: takenBy)
    return result
}