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06_removeDuplicates.swift
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06_removeDuplicates.swift
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// Remove duplicate letters from a string.
// Write a function that accepts a string as its input and
// return a string with the duplicate letters removed.
func removeDuplicatesFrom(_ input: String) -> String {
var returnString = Array(input.characters)
var i = 0
var length = returnString.count
while i < length - 1 {
if returnString[i] == returnString[i+1] {
returnString.remove(at: i+1)
length -= 1
}
i+=1
}
return String(returnString)
}
print(removeDuplicatesFrom("hello")) // helo
print(removeDuplicatesFrom("helo")) // helo
print(removeDuplicatesFrom("Helllo,, worrld!!")) // Hello, world!
// ----------------------------------------------------------
// Second approach using a for in and an additive array
func removeDuplicatesFrom2(_ input: String) -> String {
var usedCharacters = [Character]()
for letter in input.characters {
if !usedCharacters.contains(letter) {
usedCharacters.append(letter)
}
}
return String(usedCharacters)
}
print(removeDuplicatesFrom2("hello")) // helo
print(removeDuplicatesFrom2("helo")) // helo
print(removeDuplicatesFrom2("Helllo,, worrld!!")) // Helo, wrd!
// ----------------------------------------------------------
// A third solution - a functional approach using a dictionary
// (note: this solution has poor performance)
func removeDuplicatesFrom3(_ input: String) -> String {
var usedCharacters = [Character: Bool]()
let result = input.characters.filter {
usedCharacters.updateValue(true, forKey: $0) == nil
}
return String(result)
}
print(removeDuplicatesFrom3("hello")) // helo
print(removeDuplicatesFrom3("helo")) // helo
print(removeDuplicatesFrom3("Helllo,, worrld!!")) // Helo, wrd!
// Swift 4
func removeDuplicatesFrom4(_ str: String) -> String {
var usedChar = String()
str.forEach { if !usedChar.contains($0) { usedChar.append($0) }}
return usedChar
}
print(removeDuplicatesFrom4("hello")) // helo
print(removeDuplicatesFrom4("helo")) // helo
print(removeDuplicatesFrom4("Helllo,, worrld!!")) // Helo, wrd!