.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
这是一些在playground上运行的代码。你不需要在实际的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)
其他回答
swift 4.2有两个方便的功能:
// shuffles the array in place
myArray.shuffle()
and
// generates a new array with shuffled elements of the old array
let newArray = myArray.shuffled()
你也可以使用通用交换函数,实现前面提到的Fisher-Yates:
for idx in 0..<arr.count {
let rnd = Int(arc4random_uniform(UInt32(idx)))
if rnd != idx {
swap(&arr[idx], &arr[rnd])
}
}
或者更简洁:
for idx in 0..<steps.count {
swap(&steps[idx], &steps[Int(arc4random_uniform(UInt32(idx)))])
}
如果你想使用简单的Swift For循环函数,使用这个->
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)
Swift Array使用扩展名->
extension Array {
// Order Randomize
mutating func shuffle() {
for _ in 0..<count {
sort { (_,_) in arc4random() < arc4random() }
}
}
}
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
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])
}
}
}