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@junebash
Created January 29, 2020 16:59
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Unit 4 Sprint 3 - Swift Code Challenge
func commonChars(_ inputs: [String]) -> [String] {
guard let lastString = inputs.last else { return [] }
var commonCountedChars = CountedSet<String>()
for char in lastString {
commonCountedChars.add(String(char))
}
var strings = inputs
strings.removeLast()
// removing last is more computationally efficient than removing first in Swift
for string in strings {
var stringCountedChars = CountedSet<String>()
for char in string {
stringCountedChars.add(String(char))
}
for (commonChar, commonCount) in commonCountedChars.asDictionary {
if let stringCharCount = stringCountedChars.count(for: commonChar) {
if stringCharCount < commonCount {
commonCountedChars.remove(commonChar, count: commonCount - stringCharCount)
}
} else {
commonCountedChars.removeAll(of: commonChar)
}
}
}
return commonCountedChars.asArray
}
struct CountedSet<Element: Hashable> {
private var dict = [Element: UInt]()
var asArray: [Element] {
var array = [Element]()
for (element, count) in dict {
array.append(contentsOf: [Element](repeating: element, count: Int(count)))
}
return array
}
var asDictionary: [Element: UInt] { dict }
init() {}
init(from array: [Element]) {
for element in array {
if self.dict.keys.contains(element) {
self.dict[element]! += 1
} else {
self.dict[element] = 1
}
}
}
func count(for element: Element) -> UInt? {
return (dict[element] != nil) ? dict[element]! : nil
}
mutating func add(_ element: Element) {
dict[element] = (dict[element] == nil) ? 1 : dict[element]! + 1
}
mutating func remove(_ element: Element, count removingCount: UInt = 1) {
if let currentCount = dict[element] {
dict[element] = (currentCount <= removingCount) ? nil : currentCount - removingCount
}
}
mutating func removeAll(of element: Element) {
dict[element] = nil
}
}
print(commonChars(["bella","label","roller"]))
print(commonChars(["cool","lock","cook"]))
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