swift 集合类型（数组、集合、字典）

//创建一个空数组
let array = [Int]()
//创建具有默认值的数组
let arr1 = Array(repeating: 2, count: 3)  //[2, 2, 2]
//用数组字面量构造数组
let arr2: [String] = ["a","b"]
var arr3 = ["a","b"]

// 获取数组元素个数
arr2.count
//判断数组count是否等于0
if arr2.isEmpty {
    print("The arr2 is empty.")
}

//尾部添加
var arr = [Int]()
arr.append(5)
print(arr)  //[5]

//指定索引添加
var arr2: [String] = ["a","b","c","d","e","f","g"]
arr2.insert("C", at: 2)
print(arr2)
//["a", "b", "C", "c", "d", "e", "f", "g"]

var arr = [Int]()
let arr1 = Array(repeating: 2, count: 3)
arr += arr1 // arr:[2, 2, 2]

let arr2: [String] = ["a","b"]
var value = arr2[0]

var arr2: [String] = ["a","b"]
arr2[0] = "c"
print(arr2)  //["c", "b"]


var arr3: [String] = ["a","b","c","d","e","f","g"]
arr3[2...5] = ["x","y","z"]
print(arr3)  //["a", "b", "x", "y", "z", "g"]

var arr: [String] = ["a","b","c","d","e","f","g"]
arr.remove(at: 2)
print(arr)  // ["a", "b", "d", "e", "f", "g"]

arr.removeLast()
print(arr)  // ["a", "b", "d", "e", "f"]

arr.removeAll()

var arr: [String] = ["a","b","c"]
for item in arr {
    print(item)
}
for (index ,value) in arr.enumerated() {
    print("\(index)---\(value)")
}
//a
//b
//c
//0---a
//1---b
//2---c

//创建一个空集合
var set = Set<String>()
//用数组字面量构造
var set :Set<String> = ["a","b","c"]
var set :Set = ["a","b","c"]

// 获取数组元素个数
set.count
//判断数组count是否等于0
if set.isEmpty {
    print("The set is empty.")
}

var set :Set<String> = ["a","b","c"]
set.insert("d")
print(set)
//["b", "a", "d", "c", "e"]

var set :Set<String> = ["a","b","c"]
set.remove("b")
print(set)  //["c", "a"]

set.removeAll()

let set :Set<String> = ["a","b","c"]
let set1 :Set<String> = ["c","v","e","a","f","d"]
//交集
print(set.intersection(set1))
//["c", "a"]

//并集
print(set.union(set1))
//["e", "v", "b", "c", "a", "d", "f"]

//去除交集
print(set.symmetricDifference(set1))
//["e", "f", "v", "b", "d"]

//一个值不在指定集中的新集
print(set.subtracting(set1))
//["b"]

//判断一个集合中的值是否也被包含在另外一个集合中
print(set1.isSubset(of: set))   //false

//判断一个集合中包含另一个集合中所有的值
print(set1.isSuperset(of: set)) //false

//判断一个集合是否是另外一个集合的子集合或者父集合并且两个集合并不相等
print(set1.isStrictSubset(of: set))   //false

//判断两个集合是否不含有相同的值(是否没有交集)
print(set1.isStrictSubset(of: set))   //false

for value in set {
    print(value)
}
//a  c  b

//集合先排序在遍历
for genre in set.sorted() {
    print("\(genre)")
}

//构造语法
var dic = [Int: String]()
//创建具有默认值的字典
var dic : [String:String] = ["key":"value"]
var dic = ["key":"value"]

// 获取数组元素个数
var dic : [String:String] = ["key":"value","key1":"value1"]
print(dic.count)

//判断数组count是否等于0
if dic.isEmpty {
    print("the dic is empty")
}

var dic : [String:String] = ["key":"a","key1":"b"]
dic["key2"] = "c"
print(dic)  //["key1": "b", "key2": "c", "key": "a"]

//使用下标语法来改变特定键对应的值
var dic : [String:String] = ["key":"a","key1":"b"]
dic["key1"] = "B"
print(dic)  //["key": "a", "key1": "B"]

var dic : [String:String] = ["key":"a","key1":"b"]

//如果有对应的key，那么会直接更新对应的value，且返回旧值
let oldValue = dic.updateValue("C", forKey: "key1")
print(dic)  //["key1": "C", "key": "a"]
print(oldValue)    //Optional("b")

//如果没有对应的key，那么会直接添加元素，返回nil
let oldValue1 = dic.updateValue("D", forKey: "key2")
print(dic)  //["key1": "C", "key2": "D", "key": "a"]
print(oldValue1)    //nil

var dic : [String:String] = ["key":"a","key1":"b"]
dic["key1"] = nil
print(dic)  //["key": "a"]
dic.removeValue(forKey: "key1")
print(dic)  //["key": "a"]

let dic : [String:String] = ["key":"a","key1":"b"]
for (key,value) in dic {
    print("\(key)---\(value)")
}    //key---a    key1---b

for key in dic.keys {
    print("\(key)")
}    //key  key1

for value in dic.values {
    print("\(value)")
}    //a  b