这会找到数组中的重复项,但是我正在寻找可以找到字符串中第一个非重复字符的东西。我一直在试图找到一种方法来做,但我无法解决。这是我最近得到的。
var strArray = ["P","Q","R","S","T","P","R","A","T","B","C","P","P","P","P","P","C","P","P","J"]
println(strArray)
var filter = Dictionary<String,Int>()
var len = strArray.count
for var index = 0; index < len ;++index {
var value = strArray[index]
if (filter[value] != nil) {
strArray.removeAtIndex(index--)
len--
}else{
filter[value] = 1
}
}
println(strArray)
为了判断字符是否重复,请遍历整个数组一次,增加字典中出现的次数:
let characters = ["P","Q","R","S","T","P","R","A","T","B","C","P","P","P","P","P","C","P","P","J"]
var counts: [String: Int] = [:]
for character in characters {
counts[character] = (counts[character] ?? 0) + 1
}
let nonRepeatingCharacters = characters.filter({counts[$0] == 1})
// ["Q", "S", "A", "B", "J"]
let firstNonRepeatingCharacter = nonRepeatingCharacters.first!
// "Q"
func firstNonRepeatedCharacter(input: String) -> Character?{
var characterCount : [Character : Int] = [:]
var uniqueCharacter: Character?
for character in input{
if let count = characterCount[character]{
characterCount[character] = count + 1
if(uniqueCharacter == character)
{
uniqueCharacter = nil
}
}
else{
characterCount[character] = 1
if(uniqueCharacter == nil){
uniqueCharacter = character
}
}
}
return uniqueCharacter
}
没有多余的循环来从characterCount字典中查找字符
这是我发现来检测第一个非重复字符的方法。它删除空格和标点符号以查找不重复的实际字母或数字。
extension String {
func removeNonAlphaNumChars() -> String {
let charSet = NSCharacterSet.alphanumericCharacterSet().invertedSet
return self
.componentsSeparatedByCharactersInSet(charSet)
.joinWithSeparator("")
}
var firstNonRepeatedCharacter: Character? {
let alphaNumString = self.removeNonAlphaNumChars()
let characters = alphaNumString.characters
let count = characters.count
guard count > 0 else { return nil }
// Find unique chars
var dict: [Character: Int?] = [:]
for (index, char) in characters.enumerate() {
if dict[char] != nil {
dict[char] = (nil as Int?)
}
else {
dict[char] = index
}
}
return dict.filter { $0.1 != nil }.sort { $0.1 < $1.1 }.first?.0
}
}
我完全不知道为什么接受的答案被认为是正确的。他们正在使用
.first
字典的方法,根据文档的说明,它将在字典中返回一个随机元素,而不是第一个元素,因为swift中的字典没有像数组那样排序。。
请在下面找到有效的实现
func firstNonRepeatingLetter(_ str: String) -> String{
var characterDict = [String : Int]()
for character in str{
let lower = character.lowercased()
if let count = characterDict[lower]{
characterDict[lower] = count + 1
}else{
characterDict[lower] = 1
}
}
let filtered = characterDict.filter { $0.value == 1}
for character in str{
let lower = character.lowercased()
if let _ = filtered[lower]{
return lower
}
}
return ""
}
firstNonRepeatingLetter("moonmen") would return "e".