lj palindrome

.gitignore

@@ -0,0 +1 @@
+.idea

lib/palindrome_check.rb

@@ -1,5 +1,41 @@
 # A method to check if the input string is a palindrome.
 # Return true if the string is a palindrome. Return false otherwise.
 def palindrome_check(my_phrase)
-  raise NotImplementedError
+  # check for nil
+  unless my_phrase.nil?
+    i = 0
+    last = my_phrase.length - 1
+    while i < last # O(n/2)
+      # iterate from head of string until non whitespace char
+      until my_phrase[i] != ' ' # O(n/2)
+        i += 1
+      end
+
+      # iterate from tail of string until non whitespace char
+      until my_phrase[last] != ' ' # O(n/2)
+        last -= 1
+      end
+
+
+      # once two non-whitespace characters are found compare them
+      if my_phrase[i] != my_phrase[last]
+        return false
+      else
+        i += 1
+        last -= 1
+      end
+    end
+
+    return true
+  end
+
+  return false
 end
+
+# For time complexity I think the overall number of operations is dependent on the
+# length of the string/phrase (n) At most 1/2 of the length of the string
+# operations will be necessary to iterate over (the head and tail
+# increment/decrement in unison)  O(n)
+# Using this method no additional space is required beyond the
+# head and tail incrementors as all non-whitespace characters are checked in
+# place and only a boolean is returned O(n)