스위프트 문법 12 (Set)
- 6 minsSet
- Unordered Collection (정렬되지 않음)
- Unique Value (고유의 값)
- Set Literal = Array Literal
선언은 아래와 같이 한다.
let fruitsSet: Set<String> = ["Apple", "Orange", "Melon"]
let numbers: Set = [1, 2, 3, 3, 3]
let emptySet = Set<String>()
Number of Elements
value 개수를 파악하는 함수는 다른 Collection Function 처럼 .count를 사용하면 된다.
fruitsSet.count //3
if !fruitsSet.isEmpty {
print("\(fruitsSet.count) element(s)") //3 element(s)
} else {
print("empty set")
}
Searching
검색 기능역시 다른 배열들과 크게 다르지 않다.
if fruitsSet.contains("Apple") {
print("yes") //yes
}
let productSet: Set = ["iPhone", "iPad", "Mac Pro", "iPad Pro", "Macbook Pro"]
let filteredSet = productSet.filter { (element) -> Bool in
return element.hasPrefix("i")
}
filteredSet //{"iPad", "iPad Pro", "iPhone"}
Add a New Element
새로운 값을 넣고 싶을때는 .insert를 이용하면 된다.
var set: Set<String> = []
set.insert("Apple")
set //{"Apple"}
var result = set.insert("Orange")
result
set //{"Orange", "Apple"}
result = set.insert("Orange")
result
set //{"Orange", "Apple"}
Remove an Element
값을 삭제하려면 .remove, 또, 모든 값을 삭제하려면 .removeAll을 사용하면 된다.
set = ["Apple", "Orange", "Melon"]
if let removed = set.remove("Apple") {
print("\(removed) has been removed!") //Apple has been removed!
}
set //{"Orange", "Melon"}
set.removeAll(keepingCapacity: true) //Set([])
Compare two sets
두개의 set을 비교하려면
var favoriteFruits = Set(["Apple", "Orange", "Melon"])
var tropicalFruits = Set(["Orange", "Melon", "Apple"])
//순서와 상관없이 같은 값을 갖고있기 때문에 참이된다.
if favoriteFruits == tropicalFruits {
print("favoriteFruits == tropicalFruits") //favoriteFruits == tropicalFruits
} else {
print("favoriteFruits != tropicalFruits")
}
//순서가 달라 거짓이 된다.
if favoriteFruits.elementsEqual(tropicalFruits) {
print("favoriteFruits == tropicalFruits")
} else {
print("favoriteFruits != tropicalFruits") //favoriteFruits != tropicalFruits
}
Subset & Supreset
다른 Collection에는 없는 set에만 있는 집합 관련 특징이다.
a, b, c는 각각 Set이며 a는 b의 superset, b는 a의 subset, b와 c는 서로에게 disjoint한 관계이다.
“is equal” operator (==) : 두 Set의 내용이 전부 동일 (Item의 type, count, value 모두)
- isSubset(of:): subset인지를 판
- isSuperset(of:): superset인지를 판별
- isStrictSubset(of:): subset이면서, subset!=superset
- isStrictSuperset(of:): superset이면서, subset!=superset
- isDisjoint(with:): 두 Set 간의 교집합이 없음
tropicalFruits = Set(["Banana", "Papaya", "Kiwi", "Pineapple"])
let yellowFruits = Set(["Banana"])
//yellowFruits는 yellowFruits의 부분 집합인가?
if yellowFruits.isSubset(of: tropicalFruits) {
print("yellowFruits ⊂ tropicalFruits") //yellowFruits ⊂ tropicalFruits
} else {
print("yellowFruits ⊄ tropicalFruits")
}
// subset이면서, subset!=superset
if yellowFruits.isStrictSubset(of: tropicalFruits) {
print("yellowFruits ⊂ tropicalFruits")
} else {
print("yellowFruits ⊄ tropicalFruits")
}
//superset인지를 판별
if tropicalFruits.isSuperset(of: yellowFruits) {
print("tropicalFruits ⊃ yellowFruits")
} else {
print("tropicalFruits ⊅ yellowFruits")
}
//superset이면서, subset!=superset
if tropicalFruits.isStrictSuperset(of: yellowFruits) {
print("tropicalFruits ⊃ yellowFruits")
} else {
print("tropicalFruits ⊅ yellowFruits")
}
Fundamental Set Operations
- intersection
- union
- subtracting
- symmetricDifference
intersection (교집합)
//{"Kiwi"}
favoriteFruits = Set(["Apple", "Orange", "Melon", "Kiwi"])
tropicalFruits = Set(["Banana", "Papaya", "Kiwi", "Pineapple"])
if favoriteFruits.isDisjoint(with: tropicalFruits) {
print("favoriteFruits ∩ tropicalFruits = ∅")
} else {
print("favoriteFruits ∩ tropicalFruits") //favoriteFruits ∩ tropicalFruits
}
let commonSet = favoriteFruits.intersection(tropicalFruits)
commonSet
tropicalFruits.formIntersection(favoriteFruits)
tropicalFruits
union (합집합)
//{"Melon", "Kiwi", "Orange", "Apple"}
var unionSet = favoriteFruits.union(tropicalFruits)
unionSet
unionSet = Set(favoriteFruits)
unionSet.formUnion(tropicalFruits)
unionSet
subtracting (빼기)
//{"Melon", "Orange", "Apple"}
let uncommonSet = favoriteFruits.subtracting(tropicalFruits)
uncommonSet
favoriteFruits.subtract(tropicalFruits)
favoriteFruits
symmetricDifference
//{"Melon", "Kiwi", "Orange", "Apple"}
let exclusiveSet = favoriteFruits.symmetricDifference(tropicalFruits)
exclusiveSet
favoriteFruits.formSymmetricDifference(tropicalFruits)
favoriteFruits
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