.shuffle()和.shuffled()是Swift的一部分
原历史问题:
我如何随机或洗牌在Swift数组中的元素?例如,如果我的数组包含52张扑克牌,我想要洗牌数组以洗牌牌组。
.shuffle()和.shuffled()是Swift的一部分
原历史问题:
我如何随机或洗牌在Swift数组中的元素?例如,如果我的数组包含52张扑克牌,我想要洗牌数组以洗牌牌组。
当前回答
以Nate的算法为例,我想看看Swift 2和协议扩展会是什么样子。
这是我想到的。
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MutableCollectionType都可以使用这些方法,因为它使用Int作为索引
其他回答
当我将xCode版本升级到7.4 beta时,它停止在“swap(&self[i], &self[j])”。 致命错误:不支持与自身交换位置
我找到了I = j的原因(交换函数将爆炸)
所以我添加了一个条件,如下所示
if (i != j){
swap(&list[i], &list[j])
}
丫!对我来说没问题。
Swift 3解决方案,遵循@Nate Cook的回答:(如果索引从0开始,请参阅下面的评论)
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])
}
}
}
SWIFT 4
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
}
斯威夫特4 在for循环中洗牌数组的元素,其中i是混合比例
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))))
}
}
或者扩展为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
}
}
}
这是如何在Swift 3.0中洗牌一个种子数组。
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])
}
}
}