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Fisher-Yates Shuffle in Swift.
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| Source: http://stackoverflow.com/a/24029847/1855792 by Nate Cook | |
| Implementation of Fisher-Yates (fast and uniform) shuffle for any collection type using Swift 2 Protocol Extensions. | |
| The naming and behavior follow Swift 2.0's sort() and sortInPlace() methods. | |
| Code: | |
| See FisherYatesShuffle.swift file | |
| Usage: | |
| [1, 2, 3].shuffle() | |
| // [2, 3, 1] | |
| let fiveStrings = 0.stride(through: 100, by: 5).map(String.init).shuffle() | |
| // ["20", "45", "70", "30", ...] | |
| var numbers = [1, 2, 3, 4] | |
| numbers.shuffleInPlace() | |
| // [3, 2, 1, 4] |
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| 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]) | |
| } | |
| } | |
| } |
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