diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..b946402
Binary files /dev/null and b/.DS_Store differ
diff --git a/lib/.DS_Store b/lib/.DS_Store
new file mode 100644
index 0000000..ace602a
Binary files /dev/null and b/lib/.DS_Store differ
diff --git a/lib/reverse_sentence.rb b/lib/reverse_sentence.rb
index 3fe7cac..32dd24b 100644
--- a/lib/reverse_sentence.rb
+++ b/lib/reverse_sentence.rb
@@ -1,6 +1,22 @@
 # A method to reverse the words in a sentence, in place.
-# Time complexity: ?
-# Space complexity: ?
+# Time complexity: O(n)
+# Space complexity: O(1)
 def reverse_sentence(my_sentence)
-  raise NotImplementedError
+ 
+  if my_sentence == nil
+    return nil
+  elsif 
+    my_sentence == ""
+    return ""
+  end
+
+  array = my_sentence.split(/(\S*|\s*)/) # Split by each word and each space
+  i = 0
+
+  array.each do |match|
+    position = -i + my_sentence.length - match.length
+  
+    my_sentence[position...position+match.length] = match
+    i += match.length
+  end
 end
diff --git a/lib/sort_by_length.rb b/lib/sort_by_length.rb
index a5713ad..08a2e60 100644
--- a/lib/sort_by_length.rb
+++ b/lib/sort_by_length.rb
@@ -1,7 +1,25 @@
 # 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)
+# Space complexity: O(n)
+
 def sort_by_length(my_sentence)
-  raise NotImplementedError, "Method not implemented"
+  array = my_sentence.split
+  length = array.length
+  i = 0
+
+  while i < length-1 
+    j = 0
+    while j < length-i-1 
+      if array[j].length > array[j+1].length # compares the length of each word
+        temp = array[j]
+        array[j] = array[j+1]
+        array[j+1] = temp
+      end
+      j += 1
+    end
+    i += 1
+  end
+
+  return array 
 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