Randomly shuffle a Swift array

Array+Shuffle.swift

import Foundation

extension Array
{
    /** Randomizes the order of an array's elements. */
    mutating func shuffle()
    {
        for _ in 0..<10
        {
            sort { (_,_) in arc4random() < arc4random() }
        }
    }
}

var organisms = [
    "ant",  "bacteria", "cougar",
    "dog",  "elephant", "firefly",
    "goat", "hedgehog", "iguana"]

println("Original: \(organisms)")

organisms.shuffle()

println("Shuffled: \(organisms)")

Is it uniform?

thanks

Thanks! Super easy way to shuffle an array.

if an array have more than 1024 (2^10) items, this method would be inappropriate.

extension Array {
    mutating func shuffle() {
        for _ in 0..<((count>0) ? (count-1) : 0) {
            sort { (_,_) in arc4random() < arc4random() }
        }
    }
}

Quite helpful! Thanks!

why organisms? hahaha. Thanks tho!

@ZhipingYang Why not just this?

/**
 Extend array to enable random shuffling
 */
extension Array {
    /** 
     Randomizes the order of an array's elements
     */
    mutating func shuffle() {
        for _ in 0..<count {
            sort { (_,_) in arc4random() < arc4random() }
        }
    }
}

Or this:

extension Array {
    mutating func shuffle() {
        for _ in indices {
            sort { (_,_) in arc4random() < arc4random() }
        }
    }
}

@jakerockland Be careful with time complexity!

0..<count means O(n)
sort means O(nlogn)
Total complexity is O(n^2logn). That's a terrible complexity.