如何在Swift中随机或随机排列数组中的元素?例如,如果我的阵列由52张扑克牌,我想洗牌的阵列,以洗牌。
array.shuffle
。无需实现自己的版本。我猜OP正在寻找类似的东西。
如何在Swift中随机或随机排列数组中的元素?例如,如果我的阵列由52张扑克牌,我想洗牌的阵列,以洗牌。
array.shuffle
。无需实现自己的版本。我猜OP正在寻找类似的东西。
Answers:
这个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。
shuffle
并且shuffled
是Swift 4.2的原生版本。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]
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。
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。
(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]
(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
作为变异数组方法通过此扩展,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]
countElements
,然后替换count
,现在返回a,T.Index.Distance
因此约束条件为on C.Index.Distance == Int
。这个版本应该可以使用:gist.github.com/airspeedswift/03d07a9dc86fabdc370f
[1, 2].shuffled()
返回[2, 1]
吗?
if count > 0
在变异数组函数的顶部添加了代码,以防止在传递空数组时收到“致命错误:无法形成范围为end <start的Range”。
guard i != j else { continue }
在交换之前添加。我提起了雷达,但是新行为是故意的。
shuffleInPlace
如果集合索引不是从零开始的,例如对于数组切片,实际上可能会崩溃。for i in 0..<count - 1
应该是这样for i in startIndex ..< endIndex - 1
(然后向Swift 3的转换几乎变得微不足道了)。
编辑:如其他答案所述,Swift 4.2 最终将随机数生成添加到标准库,并完成了数组改组。
但是,GameplayKit中的GKRandom
/ GKRandomDistribution
套件对于新RandomNumberGenerator
协议仍然可以使用-如果您向GameplayKit RNG添加扩展以符合新的标准库协议,则可以轻松获得:
...并仍然使用Swift中新的“本机”随机API。
该答案的其余部分与此类RNG和/或它们在较早的Swift编译器中的使用有关。
这里已经有一些不错的答案,以及一些很好的说明,说明如果不注意,编写自己的随机播放为什么会容易出错。
在iOS 9,macOS 10.11和tvOS 9(或更高版本)中,您不必自己编写。有一个有效的,正确的执行费雪耶茨在GameplayKit(其中,尽管名称,不只是游戏)。
如果您只想进行独特的洗牌:
let shuffled = GKRandomSource.sharedRandom().arrayByShufflingObjects(in: array)
如果您希望能够复制随机排列或一系列随机排列,请选择一个特定的随机源并为其设定种子;例如
let lcg = GKLinearCongruentialRandomSource(seed: mySeedValue)
let shuffled = lcg.arrayByShufflingObjects(in: array)
在iOS 10 / macOS 10.12 / tvOS 10中,还有一种方便的语法,可通过扩展使用进行改组NSArray
。当然,当您使用Swift时Array
,这会有些麻烦(并且当返回Swift时,它会丢失其元素类型):
let shuffled1 = (array as NSArray).shuffled(using: random) // -> [Any]
let shuffled2 = (array as NSArray).shuffled() // use default random source
但是很容易为它创建一个保留类型的Swift包装器:
extension Array {
func shuffled(using source: GKRandomSource) -> [Element] {
return (self as NSArray).shuffled(using: source) as! [Element]
}
func shuffled() -> [Element] {
return (self as NSArray).shuffled() as! [Element]
}
}
let shuffled3 = array.shuffled(using: random)
let shuffled4 = array.shuffled()
let shuffled = lcg.arrayByShufflingObjects(in: array)
在Swift 2.0中,GameplayKit可能会抢救出来!(受iOS9或更高版本支持)
import GameplayKit
func shuffle() {
array = GKRandomSource.sharedRandom().arrayByShufflingObjectsInArray(array)
}
import GameplayKit.GKRandomSource
这可能更短一些:
sorted(a) {_, _ in arc4random() % 2 == 0}
sort
函数需要关闭才能对元素进行排序。此闭包采用两个参数(elem1,elem2),如果第一个值应出现在第二个值之前,则必须返回true,否则返回false。如果我们改为返回一个随机布尔值……那么我们
arc4random_uniform()
,因为当前受模偏差的影响。其次,输出在很大程度上取决于排序算法(如果不查看源代码,这是我们所不知道的)。
collection.sorted { _,_ in arc4random_uniform(1) == 0 }
以Nate的算法为例,我想看看Swift 2和协议扩展的外观。
这就是我想出的。
extension MutableCollectionType where Self.Index == Int {
mutating func shuffleInPlace() {
let c = self.count
for i in 0..<(c - 1) {
let j = Int(arc4random_uniform(UInt32(c - i))) + i
swap(&self[i], &self[j])
}
}
}
extension MutableCollectionType where Self.Index == Int {
func shuffle() -> Self {
var r = self
let c = self.count
for i in 0..<(c - 1) {
let j = Int(arc4random_uniform(UInt32(c - i))) + i
swap(&r[i], &r[j])
}
return r
}
}
现在,任何人MutableCollectionType
只要将其Int
用作Index
就我而言,我在交换数组中的对象时遇到了一些问题。然后我挠着头,去重新发明轮子。
// swift 3.0 ready
extension Array {
func shuffled() -> [Element] {
var results = [Element]()
var indexes = (0 ..< count).map { $0 }
while indexes.count > 0 {
let indexOfIndexes = Int(arc4random_uniform(UInt32(indexes.count)))
let index = indexes[indexOfIndexes]
results.append(self[index])
indexes.remove(at: indexOfIndexes)
}
return results
}
}
这是Nate为Swift 4 (Xcode 9)实现Fisher-Yates随机播放的版本。
extension MutableCollection {
/// Shuffle the elements of `self` in-place.
mutating func shuffle() {
for i in indices.dropLast() {
let diff = distance(from: i, to: endIndex)
let j = index(i, offsetBy: numericCast(arc4random_uniform(numericCast(diff))))
swapAt(i, j)
}
}
}
extension Collection {
/// Return a copy of `self` with its elements shuffled
func shuffled() -> [Element] {
var list = Array(self)
list.shuffle()
return list
}
}
更改为:
Indices.Iterator.Element == Index
现在,约束已成为Collection
协议的一部分,并且不再需要对扩展施加任何约束。swapAt()
集合来完成,比较SE-0173 AddMutableCollection.swapAt(_:_:)
。Element
是的别名Iterator.Element
。这是我用的:
func newShuffledArray(array:NSArray) -> NSArray {
var mutableArray = array.mutableCopy() as! NSMutableArray
var count = mutableArray.count
if count>1 {
for var i=count-1;i>0;--i{
mutableArray.exchangeObjectAtIndex(i, withObjectAtIndex: Int(arc4random_uniform(UInt32(i+1))))
}
}
return mutableArray as NSArray
}
Swift 4 在for循环中随机排列数组的元素,其中i是混合比
var cards = [Int]() //Some Array
let i = 4 // is the mixing ratio
func shuffleCards() {
for _ in 0 ..< cards.count * i {
let card = cards.remove(at: Int(arc4random_uniform(UInt32(cards.count))))
cards.insert(card, at: Int(arc4random_uniform(UInt32(cards.count))))
}
}
或带有扩展名Int
func shuffleCards() {
for _ in 0 ..< cards.count * i {
let card = cards.remove(at: cards.count.arc4random)
cards.insert(card, at: cards.count.arc4random)
}
}
extension Int {
var arc4random: Int {
if self > 0 {
print("Arc for random positiv self \(Int(arc4random_uniform(UInt32(self))))")
return Int(arc4random_uniform(UInt32(self)))
} else if self < 0 {
print("Arc for random negotiv self \(-Int(arc4random_uniform(UInt32(abs(self)))))")
return -Int(arc4random_uniform(UInt32(abs(self))))
} else {
print("Arc for random equal 0")
return 0
}
}
}
@Nate Cook回答以下的Swift 3解决方案:(如果索引以0开头,则工作,请参见下面的注释)
extension Collection {
/// Return a copy of `self` with its elements shuffled
func shuffle() -> [Generator.Element] {
var list = Array(self)
list.shuffleInPlace()
return list
} }
extension MutableCollection 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 }
let countInt = count as! Int
for i in 0..<countInt - 1 {
let j = Int(arc4random_uniform(UInt32(countInt - i))) + i
guard i != j else { continue }
swap(&self[i], &self[j])
}
}
}
var a = [1, 2, 3, 4, 5, 6][3..<6]; a.shuffleInPlace()
几次。–请参阅stackoverflow.com/a/37843901/1187415,以获取正确的解决方案。
这是最简单的方法。import Gamplaykit
到您的VC,并使用以下代码。在Xcode 8中测试。
import GameplayKit
let array: NSArray = ["Jock", "Ellie", "Sue Ellen", "Bobby", "JR", "Pamela"]
override func viewDidLoad() {
super.viewDidLoad()
print(array.shuffled())
}
如果要从数组中获取经过改组的字符串,则可以使用以下代码。
func suffleString() {
let ShuffleArray = array.shuffled()
suffleString.text = ShuffleArray.first as? String
print(suffleString.text!)
}
使用Swift 3,如果您想就地重组数组或从数组中获得新的重组数组,AnyIterator
可以为您提供帮助。这个想法是从您的数组中创建一个索引数组,用AnyIterator
实例和swap(_:_:)
函数将这些索引改组,并映射此索引的每个元素AnyIterator
与数组的对应元素。
以下Playground代码展示了其工作原理:
import Darwin // required for arc4random_uniform
let array = ["Jock", "Ellie", "Sue Ellen", "Bobby", "JR", "Pamela"]
var indexArray = Array(array.indices)
var index = indexArray.endIndex
let indexIterator: AnyIterator<Int> = AnyIterator {
guard let nextIndex = indexArray.index(index, offsetBy: -1, limitedBy: indexArray.startIndex)
else { return nil }
index = nextIndex
let randomIndex = Int(arc4random_uniform(UInt32(index)))
if randomIndex != index {
swap(&indexArray[randomIndex], &indexArray[index])
}
return indexArray[index]
}
let newArray = indexIterator.map { array[$0] }
print(newArray) // may print: ["Jock", "Ellie", "Sue Ellen", "JR", "Pamela", "Bobby"]
您可以重构先前的代码并shuffled()
在Array
扩展内创建函数,以便从数组中获取新的随机数组:
import Darwin // required for arc4random_uniform
extension Array {
func shuffled() -> Array<Element> {
var indexArray = Array<Int>(indices)
var index = indexArray.endIndex
let indexIterator = AnyIterator<Int> {
guard let nextIndex = indexArray.index(index, offsetBy: -1, limitedBy: indexArray.startIndex)
else { return nil }
index = nextIndex
let randomIndex = Int(arc4random_uniform(UInt32(index)))
if randomIndex != index {
swap(&indexArray[randomIndex], &indexArray[index])
}
return indexArray[index]
}
return indexIterator.map { self[$0] }
}
}
用法:
let array = ["Jock", "Ellie", "Sue Ellen", "Bobby", "JR", "Pamela"]
let newArray = array.shuffled()
print(newArray) // may print: ["Bobby", "Pamela", "Jock", "Ellie", "JR", "Sue Ellen"]
let emptyArray = [String]()
let newEmptyArray = emptyArray.shuffled()
print(newEmptyArray) // prints: []
作为前面代码的替代方法,您可以shuffle()
在Array
扩展内创建一个函数,以便在适当位置随机排列数组:
import Darwin // required for arc4random_uniform
extension Array {
mutating func shuffle() {
var indexArray = Array<Int>(indices)
var index = indexArray.endIndex
let indexIterator = AnyIterator<Int> {
guard let nextIndex = indexArray.index(index, offsetBy: -1, limitedBy: indexArray.startIndex)
else { return nil }
index = nextIndex
let randomIndex = Int(arc4random_uniform(UInt32(index)))
if randomIndex != index {
swap(&indexArray[randomIndex], &indexArray[index])
}
return indexArray[index]
}
self = indexIterator.map { self[$0] }
}
}
用法:
var mutatingArray = ["Jock", "Ellie", "Sue Ellen", "Bobby", "JR", "Pamela"]
mutatingArray.shuffle()
print(mutatingArray) // may print ["Sue Ellen", "Pamela", "Jock", "Ellie", "Bobby", "JR"]
您还可以使用泛型swap
函数并实现提到的Fisher-Yates:
for idx in 0..<arr.count {
let rnd = Int(arc4random_uniform(UInt32(idx)))
if rnd != idx {
swap(&arr[idx], &arr[rnd])
}
}
或更详细:
for idx in 0..<steps.count {
swap(&steps[idx], &steps[Int(arc4random_uniform(UInt32(idx)))])
}
作品!!。生物是要洗牌的阵列。
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"]
print("Original: \(organisms)")
organisms.shuffle()
print("Shuffled: \(organisms)")
在Swift 4.2中,现在有一种用于可变shuffle
和不可变的方法shuffled
。您可以在此处阅读有关随机数生成和数组内容的更多信息。
这是在Swift 3.0中使用种子将一个数组改组的方法。
extension MutableCollection where Indices.Iterator.Element == Index {
mutating func shuffle() {
let c = count
guard c > 1 else { return }
for (firstUnshuffled , unshuffledCount) in zip(indices, stride(from: c, to: 1, by: -1)) {
srand48(seedNumber)
let number:Int = numericCast(unshuffledCount)
let r = floor(drand48() * Double(number))
let d: IndexDistance = numericCast(Int(r))
guard d != 0 else { continue }
let i = index(firstUnshuffled, offsetBy: d)
swap(&self[firstUnshuffled], &self[i])
}
}
}
let shuffl = GKRandomSource.sharedRandom().arrayByShufflingObjects(in: arrayObject)
这是我用的:
import GameplayKit
extension Collection {
func shuffled() -> [Iterator.Element] {
let shuffledArray = (self as? NSArray)?.shuffled()
let outputArray = shuffledArray as? [Iterator.Element]
return outputArray ?? []
}
mutating func shuffle() {
if let selfShuffled = self.shuffled() as? Self {
self = selfShuffled
}
}
}
// Usage example:
var numbers = [1,2,3,4,5]
numbers.shuffle()
print(numbers) // output example: [2, 3, 5, 4, 1]
print([10, "hi", 9.0].shuffled()) // output example: [hi, 10, 9]
简单的例子:
extension Array {
mutating func shuffled() {
for _ in self {
// generate random indexes that will be swapped
var (a, b) = (Int(arc4random_uniform(UInt32(self.count - 1))), Int(arc4random_uniform(UInt32(self.count - 1))))
if a == b { // if the same indexes are generated swap the first and last
a = 0
b = self.count - 1
}
swap(&self[a], &self[b])
}
}
}
var array = [1,2,3,4,5,6,7,8,9,10]
array.shuffled()
print(array) // [9, 8, 3, 5, 7, 6, 4, 2, 1, 10]
不建议使用最高答案,因此我自己创建了自己的扩展以在最新版本的Swift 4.1(Xcode 9)中对数组进行随机组合:
extension Array {
// Non-mutating shuffle
var shuffled : Array {
let totalCount : Int = self.count
var shuffledArray : Array = []
var count : Int = totalCount
var tempArray : Array = self
for _ in 0..<totalCount {
let randomIndex : Int = Int(arc4random_uniform(UInt32(count)))
let randomElement : Element = tempArray.remove(at: randomIndex)
shuffledArray.append(randomElement)
count -= 1
}
return shuffledArray
}
// Mutating shuffle
mutating func shuffle() {
let totalCount : Int = self.count
var shuffledArray : Array = []
var count : Int = totalCount
var tempArray : Array = self
for _ in 0..<totalCount {
let randomIndex : Int = Int(arc4random_uniform(UInt32(count)))
let randomElement : Element = tempArray.remove(at: randomIndex)
shuffledArray.append(randomElement)
count -= 1
}
self = shuffledArray
}
}
[Array] -> [Array]
:let array = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
print(array.shuffled)
这array
将以随机顺序打印。
[Array] = [Array]
:var array = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
array.shuffle()
// The array has now been mutated and contains all of its initial
// values, but in a randomized shuffled order
print(array)
这将array
按其当前顺序打印,该顺序已经随机打乱。
希望这对每个人都有用,如果您有任何问题,建议或意见,请随时提问!
在SWIFT 4中
func createShuffledSequenceOfNumbers(max:UInt)->[UInt] {
var array:[UInt]! = []
var myArray:[UInt]! = []
for i in 1...max {
myArray.append(i)
}
for i in 1...max {
array.append(i)
}
var tempArray:[Int]! = []
for index in 0...(myArray.count - 1) {
var isNotFinded:Bool = true
while(isNotFinded){
let randomNumber = arc4random_uniform(UInt32(myArray.count))
let randomIndex = Int(randomNumber)
if(!tempArray.contains(randomIndex)){
tempArray.append(randomIndex)
array[randomIndex] = myArray[index]
isNotFinded = false
}
}
}
return array
}
如果要使用简单的Swift For循环函数,请使用此->
var arrayItems = ["A1", "B2", "C3", "D4", "E5", "F6", "G7", "H8", "X9", "Y10", "Z11"]
var shuffledArray = [String]()
for i in 0..<arrayItems.count
{
let randomObject = Int(arc4random_uniform(UInt32(items.count)))
shuffledArray.append(items[randomObject])
items.remove(at: randomObject)
}
print(shuffledArray)
使用扩展的Swift Array Suffle->
extension Array {
// Order Randomize
mutating func shuffle() {
for _ in 0..<count {
sort { (_,_) in arc4random() < arc4random() }
}
}
}
这是在操场上运行的一些代码。您无需在实际的Xcode项目中导入Darwin。
import darwin
var a = [1,2,3,4,5,6,7]
func shuffle<ItemType>(item1: ItemType, item2: ItemType) -> Bool {
return drand48() > 0.5
}
sort(a, shuffle)
println(a)
drand48()
每次都还提供相同的伪随机数,除非您设置类似的种子srand48(Int(arc4random()))