Palindrome.swift

import Foundation

func palindrom(_ string: String) -> Bool{
    let strippedString = string.replacingOccurrences(of: "\\W", with: "", options: .regularExpression, range: nil)
    let length = strippedString.characters.count
    
    if length == 0 {
        return true
    }else if length > 1{
        return isPalindrom(strippedString.lowercased(), left: 0, right: length-1)
    }else{
        return false
    }
}

private func isPalindrom(_ string: String, left:Int, right:Int) -> Bool{
    if left >= right{
        return true
    }
    
    let lhs = string[string.index(string.startIndex, offsetBy: left)]
    let rhs = string[string.index(string.startIndex, offsetBy: right)]
    
    if lhs != rhs{
        return false
    }
    return isPalindrom(string, left: left+1, right: right-1)
}