Katrina - Edges - Reverse Sentence

lib/reverse_sentence.rb

@@ -1,4 +1,65 @@
 # A method to reverse the words in a sentence, in place.
 def reverse_sentence(my_sentence)
+  return if my_sentence == nil || my_sentence == ''
+
+  i = 0
+  end_of_s = my_sentence.length - 1
+
+  # reverse the whole sentence
+  reverse_string(my_sentence, i, end_of_s)
+
+  # reverse the words
+  reverse_words(my_sentence)
+
+  return
   raise NotImplementedError
 end
+
+
+def reverse_words(my_words)
+  i = 0
+  all_words_end = my_words.length
+
+  while i < all_words_end
+
+    while my_words[i] == ' ' && i < all_words_end
+      i += 1
+    end
+    start_of_word = i
+
+    while my_words[i] != ' ' && i < all_words_end
+      i += 1
+    end
+    end_of_word = i - 1
+
+    reverse_string(my_words, start_of_word, end_of_word)
+  end
+
+  return my_words
+  raise NotImplementedError
+end
+
+def reverse_string(string, start_of_word, end_of_word)
+
+  i = start_of_word
+  j = end_of_word
+
+  while i < j
+    temp = string[i]
+    string[i] = string[j]
+    string[j] = temp
+
+    i += 1
+    j -= 1
+  end
+
+  return string
+end
+
+
+=begin
+Time complexity is linear O(3n), where n is the length of the input(my_sentence)
+
+Space complexity is constant O(1), because the storage remains the same
+even if the input (my_sentece) increases.
+=end