Find Duplicate Elements In Array Using Swift

Question

How to find Duplicate Elements in Array? I have array of phone numbers so in the phone numbers i should start searching from the right side to the left side and find similar

Answer 1

extension Array where Element: Hashable {
     func similar() -> Self {
        var used = [Element: Bool]()

        return self.filter { used.updateValue(true, forKey: $0) != nil }
    }
}