Palindromes swift file, playground, and README file added

Author: Stephen Rutstein

Palindromes/Palindromes.playground/Contents.swift

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+import Cocoa
+
+public func palindromeCheck (text: String?) -> Bool {
+  if let text = text {
+    let mutableText = text.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet()).lowercaseString
+    let length: Int = mutableText.characters.count
+    
+    if length < 1 {
+      return false
+    }
+    
+    if length == 1 {
+      return true
+    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.endIndex.predecessor()] {
+      let range = Range<String.Index>(mutableText.startIndex.successor()..<mutableText.endIndex.predecessor())
+      return palindromeCheck(mutableText.substringWithRange(range))
+    }
+  }
+  
+  return false
+}
+
+// Test to check that non-palindromes are handled correctly:
+palindromeCheck("owls")
+
+// Test to check that palindromes are accurately found (regardless of case and whitespace:
+palindromeCheck("lol")
+palindromeCheck("race car")
+palindromeCheck("Race fast Safe car")
+
+// Test to check that palindromes are found regardless of case:
+palindromeCheck("HelloLLEH")
+
+// Test that nil and empty Strings return false:
+palindromeCheck("")
+palindromeCheck(nil)

Palindromes/Palindromes.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='osx'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

Palindromes/Palindromes.swift

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+import Cocoa
+
+public func palindromeCheck (text: String?) -> Bool {
+  if let text = text {
+    let mutableText = text.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet()).lowercaseString
+    let length: Int = mutableText.characters.count
+    
+    if length < 1 {
+      return false
+    }
+    
+    if length == 1 {
+      return true
+    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.endIndex.predecessor()] {
+      let range = Range<String.Index>(mutableText.startIndex.successor()..<mutableText.endIndex.predecessor())
+      return palindromeCheck(mutableText.substringWithRange(range))
+    }
+  }
+  
+  return false
+}

Palindromes/README.markdown

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+# Palindromes
+
+A palindrome is a word or phrase that is spelled the exact same when read forwards or backwards. 
+For this example puzzle, palindromes will not take case into account, meaning that uppercase and
+lowercase text will be treated the same. In addition, spaces will not be considered, allowing 
+for multi-word phrases to constitute palindromes too. 
+
+Algorithms that check for palindromes are a common programming interview question. 
+
+## Example 
+
+The word "radar" is spelled the exact same both forwards and backwards, and as a result is a palindrome. 
+The phrase "race car" is another common palindrome that is spelled the same forwards and backwards. 
+
+## Algorithm 
+
+To check for palindromes, the first and last characters of a String must be compared for equality. 
+When the first and last characters are the same, they are removed from the String, resulting in a 
+substring starting with the second character and ending at the second to last character. 
+
+In this implementation of a palindrome checker, recursion is used to check each substring of the 
+original String. 
+
+## The code 
+
+Here is a recursive implementation of this in Swift: 
+
+``swift
+func palindromeCheck (text: String?) -> Bool {
+  if let text = text {
+    let mutableText = text.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet()).lowercaseString
+    let length: Int = mutableText.characters.count
+    
+    if length < 1 {
+      return false
+    }
+
+    if length == 1 {
+      return true
+    } else if mutableText[mutableText.startIndex] == mutableText[mutableText.endIndex.predecessor()] {
+      let range = Range<String.Index>(mutableText.startIndex.successor()..<mutableText.endIndex.predecessor())
+      return palindromeCheck(mutableText.substringWithRange(range))
+    }
+  }
+
+  return false
+}
+``
+
+
+This code can be tested in a playground using the following: 
+
+``swift
+palindromeCheck("Race car")
+``
+
+Since the phrase "Race car" is a palindrome, this will return true. 
+
+## Additional Resources
+
+[Palindrome Wikipedia](https://en.wikipedia.org/wiki/Palindrome)
+
+
+*Written by [Stephen Rutstein](https://github.com/srutstein21)*