func isPalindrome(s: String) -> Bool {
    return s == String(s.characters.reverse())
}

// Recursive
func isPalindrome2(s: String) -> Bool {
    if (s.characters.count <= 1) { return true }

    if (s[s.startIndex] != s[s.endIndex.predecessor()]) { return  false }

    return isPalindrome2(s[s.startIndex.successor()..<s.endIndex.predecessor()])
}