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I have two arrays that I want to shuffle. These are the two arrays:

var allCards = ["2_of_clubs", "2_of_spades", "2_of_diamonds", "2_of_hearts", "3_of_clubs", "3_of_spades", "3_of_diamonds", "3_of_hearts", "4_of_clubs", "4_of_spades", "4_of_diamonds", "4_of_hearts", "5_of_clubs", "5_of_spades", "5_of_diamonds", "5_of_hearts", "6_of_clubs", "6_of_spades", "6_of_diamonds", "6_of_hearts", "7_of_clubs", "7_of_spades","7_of_diamonds","7_of_hearts", "8_of_clubs", "8_of_spades", "8_of_diamonds", "8_of_hearts", "9_of_clubs", "9_of_spades", "9_of_diamonds", "9_of_hearts", "10_of_clubs", "10_of_spades", "10_of_diamonds", "10_of_hearts", "jack_of_clubs", "jack_of_spades", "jack_of_diamonds", "jack_of_hearts", "queen_of_clubs", "queen_of_spades", "queen_of_diamonds", "queen_of_hearts", "king_of_clubs", "king_of_spades", "king_of_diamonds", "king_of_hearts", "ace_of_clubs", "ace_of_spades", "ace_of_diamonds", "ace_of_hearts"]

var allValues = [2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14]

I want to shuffle them equally, so value 2 stays at 2 of clubs, 2 of spades and so on. I tried using the answers from Shuffle array swift 3 and How do I shuffle an array in Swift? they stated this should work:

let randomIndex = UInt64(arc4random_uniform(UInt32(1000)))
let randomShuffle = GKLinearCongruentialRandomSource(seed: randomIndex)
let shuffledValues = randomShuffle.arrayByShufflingObjects(in: allValues)
let shuffledCards = randomShuffle.arrayByShufflingObjects(in: allCards)
print(shuffledValues)
print(shuffledCards)

I get this as a print:

[3, 6, 5, 5, 9, 10, 11, 11, 8, 6, 5, 3, 14, 12, 3, 8, 2, 3, 10, 4, 13, 12, 7, 12, 10, 5, 12, 13, 14, 11, 2, 6, 9, 7, 10, 14, 7, 8, 6, 14, 4, 9, 13, 2, 11, 9, 4, 7, 8, 2, 13, 4]
[jack_of_clubs, 6_of_hearts, 10_of_hearts, 6_of_spades, king_of_hearts, 5_of_spades, 5_of_hearts, ace_of_diamonds, queen_of_diamonds, 10_of_spades, 7_of_hearts, queen_of_spades, 9_of_clubs, 2_of_diamonds, 3_of_hearts, 3_of_diamonds, 9_of_spades, queen_of_clubs, 8_of_clubs, 9_of_diamonds, 7_of_clubs, 3_of_spades, 8_of_spades, 8_of_hearts, 5_of_clubs, 6_of_diamonds, ace_of_spades, 2_of_spades, ace_of_clubs, 10_of_diamonds, 4_of_spades, 2_of_clubs, 10_of_clubs, king_of_diamonds, 7_of_diamonds, 6_of_clubs, 8_of_diamonds, queen_of_hearts, 9_of_hearts, jack_of_diamonds, 2_of_hearts, king_of_clubs, jack_of_spades, 4_of_hearts, 7_of_spades, 3_of_clubs, 4_of_diamonds, 4_of_clubs, king_of_spades, jack_of_hearts, ace_of_hearts, 5_of_diamonds]

Both have the same count. I am curious why this does not work. Is it possible to edit this code to make it work, else I would like to know how to shuffle an array and replicate that.

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NoKey
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    Either change your two arrays to be a single array of tuples/structs each containing a card and its associated value or create two `GKLinearCongruentialRandomSource` objects with the same seed and use each one to shuffle one array. – dan Mar 06 '17 at 20:09
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    @dan's point is definitely important. Almost always if you find yourself wanting to do this, your data structure is incorrect, and you really meant to have a single array of structs rather than two arrays of properties. You may be interested in https://www.youtube.com/watch?v=_S6UOrwS-Tg. In particular, skip to 7:12, and you may find the question familiar. – Rob Napier Mar 06 '17 at 20:21
  • Ah, yes, that was clear. I will move to a struc instead of holding two arrays. – NoKey Mar 06 '17 at 20:37

1 Answers1

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You can pair up your elements with zip, then shuffle, then unzip.

let pairs = Array(zip(allCards, allValues))

let randomIndex = UInt64(arc4random_uniform(UInt32(1000)))
let randomShuffle = GKLinearCongruentialRandomSource(seed: randomIndex)
let shuffledPairs = randomShuffle.arrayByShufflingObjects(in: pairs) as! [(String, Int)]

let shuffledCards = shuffledPairs.map { $0.0 }
let shuffledValues = shuffledPairs.map { $0.1 }
BallpointBen
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