Swift3.0 - 集合

 var letters = Set<Character>()
 var favoriteGenres: Set<String> = ["Rock", "Classical", "Hip hop"]
 var favoriteGenres: Set = ["Rock", "Classical", "Hip hop"]// 类型推断

letters = []
letters.removeAll()

letters.insert("a")

if favoriteGenres.isEmpty {}

favoriteGenres.insert("Jazz")

 if let removedGenre = favoriteGenres.remove("Rock") {
    print("\\(removedGenre)? I'm over it.")
  } else {
    print("I never much cared for that.")
}

 if favoriteGenres.contains("Funk") {
    print("I get up on the good foot.")
} else {
    print("It's too funky in here.")
}

 for genre in favoriteGenres {
   print("\\(genre)")
}

let  favoriteGenres:Set = ["A","B","C","G","D"]
for genre in favoriteGenres.sorted(by: >) {
      print("\\(genre)")
 }

let oddDigits: Set = [1, 3, 5, 7, 9]
let evenDigits: Set = [0, 2, 4, 6, 8]
let singleDigitPrimeNumbers: Set = [2, 3, 5, 7]
// 并集
oddDigits.union(evenDigits).sorted()
// // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
// 交集
 oddDigits.intersection(evenDigits).sorted()
// []
oddDigits.subtracting(singleDigitPrimeNumbers).sorted()
  // 子集
oddDigits.symmetricDifference(singleDigitPrimeNumbers).sorted()
  //补集

let houseAnimals: Set = ["", ""]
let farmAnimals: Set = ["", "", "", "", ""]
let cityAnimals: Set = ["", ""]

houseAnimals.isSubset(of: farmAnimals)
// true
farmAnimals.isSuperset(of: houseAnimals)
// true
farmAnimals.isDisjoint(with: cityAnimals)