Update palindrome playground

Palindromes/Palindromes.playground/Contents.swift

@@ -1,34 +1,61 @@
-import Cocoa
+//: Playground - noun: a place where people can play
 
-public func palindromeCheck(text: String?) -> Bool {
-  if let text = text {
-    let mutableText = text.trimmingCharacters(in: NSCharacterSet.whitespaces).lowercased()
-    let length: Int = mutableText.characters.count
+import Foundation
+
+/**
+ Validate that a string is a plaindrome
+ - parameter str: The string to validate
+ - returns: `true` if string is plaindrome, `false` if string is not
+ */
+func isPalindrome(_ str: String) -> Bool {
+    let strippedString = str.replacingOccurrences(of: "\\W", with: "", options: .regularExpression, range: nil)
+    let length = strippedString.characters.count
 
-    if length == 1 || length == 0 {
-      return true
-    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.index(mutableText.endIndex, offsetBy: -1)] {
-      let range = Range<String.Index>(mutableText.index(mutableText.startIndex, offsetBy: 1)..<mutableText.index(mutableText.endIndex, offsetBy: -1))
-      return palindromeCheck(text: mutableText.substring(with: range))
+    if length > 1 {
+        return palindrome(strippedString.lowercased(), left: 0, right: length - 1)
     }
-  }
-
-  return false
+    return false
 }
 
-// Test to check that non-palindromes are handled correctly:
-palindromeCheck(text: "owls")
-
-// Test to check that palindromes are accurately found (regardless of case and whitespace:
-palindromeCheck(text: "lol")
-palindromeCheck(text: "race car")
-palindromeCheck(text: "Race fast Safe car")
-
-// Test to check that palindromes are found regardless of case:
-palindromeCheck(text: "HelloLLEH")
+/**
+ Compares a strings left side character against right side character following
+ - parameter str: The string to compare characters of
+ - parameter left: Index of left side to compare, must be less than or equal to right
+ - parameter right: Index of right side to compare, must be greater than or equal to left
+ - returns: `true` if left side and right side have all been compared and they all match, `false` if a left and right aren't equal
+ */
+private func palindrome(_ str: String, left: Int, right: Int) -> Bool {
+    if left >= right {
+        return true
+    }
+
+    let lhs = str[str.index(str.startIndex, offsetBy: left)]
+    let rhs = str[str.index(str.startIndex, offsetBy: right)]
+
+    if lhs != rhs {
+        return false
+    }
+
+    return palindrome(str, left: left + 1, right: right - 1)
+}
 
-palindromeCheck(text: "moom")
+//true
+isPalindrome("A man, a plan, a canal, Panama!")
+isPalindrome("abbcbba")
+isPalindrome("racecar")
+isPalindrome("Madam, I'm Adam")
+isPalindrome("Madam in Eden, I'm Adam")
+isPalindrome("Never odd or even")
+isPalindrome("5885")
+isPalindrome("5 8 8 5")
+isPalindrome("58 85")
+isPalindrome("৯৯")
+isPalindrome("In girum imus nocte et consumimur igni")
 
-// Test that nil and empty Strings return false:
-palindromeCheck(text: "")
-palindromeCheck(text: nil)
+// false
+isPalindrome("\\\\")
+isPalindrome("desserts")
+isPalindrome("😀😀")
+isPalindrome("")
+isPalindrome("a")
+isPalindrome("power")