internal var endIndex: String.Index { @inline(__always) get { return Index(encodedOffset: self.count) } //count 不是String 的count } } 即指向了内存地址的起始和结束。 计算字符串的长度 String的长度,根据文档说,不可以在O(1)时间内获得,因为要遍历整个字符串。string遵守BidirectionalCollection,而不...
每一个String值都有相关的索引类型String.Index,它用于表示每个Character在字符串中的位置。 startIndex属性表示String中第一个Character的位置;endIndex表示String中最后一个字符后面的那个位置。 endIndex属性并不是字符串下标脚本的合法实际参数。 如果String为空,则String和endIndex相等。
internal typealias Index = String.Index @inlinable internal var startIndex: String.Index { @inline(__always) get { return Index(encodedOffset: 0) } } @inlinable internal var endIndex: String.Index { @inline(__always) get { return Index(encodedOffset: self.count) } //count 不是String 的...
fileprivatestaticfunc_convertFromSnakeCase(_ stringKey:String)->String{guard!stringKey.isEmptyelse{returnstringKey}// Find the first non-underscore characterguardletfirstNonUnderscore=stringKey.index(where:{$0!="_"})else{// Reached the end without finding an _returnstringKey}// Find the last non...
1classSolution {2func decodeAtIndex(_ S: String, _ K: Int) ->String {3varK =K4varN:Int =05vararrS:[Character] =Array(S)6varcountS:Int = S.count < K ?S.count : K7foriin0..<countS8{9let num:Int =arrS[i].ascii10N = num >=48&& num <=57? N * (num -48) : N +111...
[String: Any]. To get anArrayvalue from a JSON array type, conditionally cast it as[Any](or an array with a more specific element type, like[String]). You can extract a dictionary value by key or an array value by index using type cast optional binding with subscript accessors or ...
varch:Character="a"varemptyString=""// 空字符串字面量varanotherEmptyString=String()// 初始化 String 实例 // 两个字符串均为空并等价。 // 通过检查其Boolean类型的isEmpty属性来判断该字符串是否为空ifemptyString.isEmpty{print("什么都没有")}// 打印输出:"什么都没有"letunusualMenagerie="Koala...
(at: a.startIndex) //获取keys values let keyList = [String](a.keys) let valueList = [String](a.values) //过滤 a.filter { (key, value) -> Bool in if (key == "a") { return false } return true } //循环遍历 for (key,value) in a { //循环出key和value print(key + ":...
isEmpty else { assertionFailure("Unexpected empty string") return } // ... } func transformedItem(atIndex index: Int, from items: [Item]) -> Item { precondition(index >= 0 && index < items.count) // It's impossible to continue executing if the precondition has failed. // ... } ...
{ var number : Int init(_ n:Int) { self.number = n } subscript(ix:Int) -> Int { get { let s = String(self.number) return String(Array(s)[ix]).toInt()! } set { var arr = Array(String(self.number)) arr[ix] = Character(String(newValue)) self.number = String(arr).to...