Swift 2.0 shuffle / shuffleInPlace

shuffle.swift

// (c) 2015 Nate Cook, licensed under the MIT license
//
// Fisher-Yates shuffle as protocol extensions

extension CollectionType {
    /// Return a copy of `self` with its elements shuffled
    func shuffle() -> [Generator.Element] {
        var list = Array(self)
        list.shuffleInPlace()
        return list
    }
}

extension MutableCollectionType where Index == Int {
    /// Shuffle the elements of `self` in-place.
    mutating func shuffleInPlace() {
        // empty and single-element collections don't shuffle
        if count < 2 { return }

        for i in 0..<count - 1 {
            let j = Int(arc4random_uniform(UInt32(count - i))) + i
            guard i != j else { continue }
            swap(&self[i], &self[j])
        }
    }
}

[1, 2, 3].shuffle()
// [2, 3, 1]

let fiveStrings = stride(from: 0, through: 100, by: 5).map(String.init).shuffle()
// ["20", "45", "70", "30", ...]

var numbers = [1, 2, 3, 4]
numbers.shuffleInPlace()
// [3, 2, 1, 4]

Thanks, I see that we can use tuple shuffle, too http://www.fantageek.com/blog/2015/11/27/tuple-shuffle-in-swift/

if (count -1) > 2147483647 then line 21 will crash on 32Bit devices.

Hello natecook1000,

First of all thank you for sharing this shuffle in place extension it was just what I was look for to apply on an app I'm working on. It works wonderfully, thanks.

However, I just updated my project to swift 3 and changes the script to the following:

extension MutableCollection where Index == Int {
mutating func shuffleInPlace() {
if count < 2 { return}
for i in 0..< count - 1 {
let j = Int(arc4random_uniform(UInt32(count - i))) + i
guard i != j else {continue}
swap(&self[i], &self[j])
}
}
}

Only difference is that Instead of "MutableCollectionType" its "MutableCollection", and it then marks an error on the extension. It says: On the.. for i in 0..< count - 1 (Line) : Bainary operator '..>' cannot be applied to operands of type 'Int' or 'self.IndexDistance'.

Please can you fix the extension to work on swift 3. Or tell me how to fix it.

This just got nerfed in Swift 3.0. "count" is no longer available.

https://stackoverflow.com/questions/37843647/shuffle-array-swift-3