diff --git a/lib/practice_exercises.rb b/lib/practice_exercises.rb
index 291e4e6..cc54ae9 100644
--- a/lib/practice_exercises.rb
+++ b/lib/practice_exercises.rb
@@ -1,13 +1,30 @@
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: O(1)
 def remove_duplicates(list)
-  raise NotImplementedError, "Not implemented yet"
+  if list.length == 0
+    return 0
+  end
+  unique_items = 1
+  list.length.times do |index|
+    if index != 0 && list[index - 1] != list[index]
+      unique_items +=1
+    end
+  end
+  return unique_items
 end
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Did not have time to complete all the way
+
+# Time Complexity: O(n^2)
+# Space Complexity: O(n) 
 def longest_prefix(strings)
-  raise NotImplementedError, "Not implemented yet"
+  prefix_string = ""
+  strings.first.length.times do |index|
+    string.each do |string|
+      string[index]
+    end
+    return prefix_string
+  end
 end