diff --git a/lib/reverse_sentence.rb b/lib/reverse_sentence.rb
index 3fe7cac..e23ce80 100644
--- a/lib/reverse_sentence.rb
+++ b/lib/reverse_sentence.rb
@@ -1,6 +1,35 @@
 # A method to reverse the words in a sentence, in place.
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n), because we check at most 2 times each character.
+# Space complexity: O(1), variables are always constant.
+
 def reverse_sentence(my_sentence)
-  raise NotImplementedError
+  if my_sentence == nil
+    return my_sentence
+  end
+
+  reverse(my_sentence, 0, my_sentence.length - 1)
+  index = 0
+  first = 0
+  my_sentence.each_char  do |character|
+    if character == " "
+      reverse(my_sentence, first, index - 1)
+      first = index + 1
+    end
+    index += 1
+  end
+  reverse(my_sentence, first ,my_sentence.length - 1)
 end
+
+def reverse(string,first,last)
+  memo = 0
+  i = first
+  j = last
+  while i < j 
+    memo = string[i]
+    string[i] = string[j]
+    string[j] = memo
+    i += 1
+    j -= 1
+  end
+end
+
diff --git a/lib/sort_by_length.rb b/lib/sort_by_length.rb
index a5713ad..b44d3a9 100644
--- a/lib/sort_by_length.rb
+++ b/lib/sort_by_length.rb
@@ -1,7 +1,19 @@
 # A method which will return an array of the words in the string
 #  sorted by the length of the word.
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n^2) as there are two loops that depend on the size of the elements.
+# Space complexity: O(n) as I'm creating a new array.
 def sort_by_length(my_sentence)
-  raise NotImplementedError, "Method not implemented"
+    my_sentence = my_sentence.split(" ")
+    i = 1
+    while i < my_sentence.length
+      to_insert = my_sentence[i]
+      j = i
+      while j > 0 && my_sentence[j-1].length > to_insert.length
+        my_sentence[j] = my_sentence[j-1]
+        my_sentence[j-1] = to_insert
+        j -= 1
+      end
+      i += 1
+    end
+    return my_sentence
 end
diff --git a/test/sort_by_length.rb b/test/sort_by_length_test.rb
similarity index 100%
rename from test/sort_by_length.rb
rename to test/sort_by_length_test.rb