如何在Swift中对数组进行混洗？

该答案详细说明了如何在Swift 4.2+中使用快速统一的算法（Fisher-Yates）进行改组，以及如何在各个早期版本的Swift中添加相同的功能。每个Swift版本的命名和行为都与该版本的变异和非变异排序方法匹配。

迅捷4.2+ shuffle并且shuffled是原生的Swift 4.2。用法示例：

let x = [1, 2, 3].shuffled() // x == [2, 3, 1]

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

var numbers = [1, 2, 3, 4] numbers.shuffle() // numbers == [3, 2, 1, 4] Swift 4.0和4.1 这些扩展将shuffle()方法添加到任何可变集合（数组和不安全的可变缓冲区），并shuffled()在任何序列上添加方法：

extension MutableCollection { /// Shuffles the contents of this collection. mutating func shuffle() { let c = count guard c > 1 else { return }

    for (firstUnshuffled, unshuffledCount) in zip(indices, stride(from: c, to: 1, by: -1)) {
        // Change `Int` in the next line to `IndexDistance` in < Swift 4.1
        let d: Int = numericCast(arc4random_uniform(numericCast(unshuffledCount)))
        let i = index(firstUnshuffled, offsetBy: d)
        swapAt(firstUnshuffled, i)
    }
}

}

extension Sequence { /// Returns an array with the contents of this sequence, shuffled. func shuffled() -> [Element] { var result = Array(self) result.shuffle() return result } } 与上述Swift 4.2示例中的用法相同。

迅捷3 这些扩展将shuffle()方法添加到任何可变集合中，并将shuffled()方法添加到任何序列中：

extension MutableCollection where Indices.Iterator.Element == Index { /// Shuffles the contents of this collection. mutating func shuffle() { let c = count guard c > 1 else { return }

    for (firstUnshuffled , unshuffledCount) in zip(indices, stride(from: c, to: 1, by: -1)) {
        // Change `Int` in the next line to `IndexDistance` in < Swift 3.2
        let d: Int = numericCast(arc4random_uniform(numericCast(unshuffledCount)))
        guard d != 0 else { continue }
        let i = index(firstUnshuffled, offsetBy: d)
        self.swapAt(firstUnshuffled, i)
    }
}

}

extension Sequence { /// Returns an array with the contents of this sequence, shuffled. func shuffled() -> [Iterator.Element] { var result = Array(self) result.shuffle() return result } } 与上述Swift 4.2示例中的用法相同。

迅捷2 （过时的语言：自2018年7月起，您将无法使用Swift 2.x在iTunes Connect上发布）

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

}

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

[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] 斯威夫特1.2 （过时的语言：自2018年7月起，您将无法使用Swift 1.x在iTunes Connect上发布）

shuffle 作为变异数组方法 此扩展使您可以Array在适当的位置随机排列一个可变实例：

extension Array { mutating func shuffle() { if count < 2 { return } for i in 0..<(count - 1) { let j = Int(arc4random_uniform(UInt32(count - i))) + i swap(&self[i], &self[j]) } } } var numbers = [1, 2, 3, 4, 5, 6, 7, 8] numbers.shuffle() // e.g., numbers == [6, 1, 8, 3, 2, 4, 7, 5] shuffled 作为非变异数组方法 通过此扩展，您可以检索Array实例的随机组合副本：

extension Array { func shuffled() -> [T] { if count < 2 { return self } var list = self for i in 0..<(list.count - 1) { let j = Int(arc4random_uniform(UInt32(list.count - i))) + i swap(&list[i], &list[j]) } return list } } let numbers = [1, 2, 3, 4, 5, 6, 7, 8] let mixedup = numbers.shuffled() // e.g., mixedup == [6, 1, 8, 3, 2, 4, 7, 5] 问题来源于stack overflow