diff --git a/lib/practice_exercises.rb b/lib/practice_exercises.rb
index 291e4e6..7aa213a 100644
--- a/lib/practice_exercises.rb
+++ b/lib/practice_exercises.rb
@@ -1,13 +1,45 @@
-
-# Time Complexity: ?
-# Space Complexity: ?
+require 'pry'
+# Time Complexity: O(n)
+# Space Complexity: O(n)
 def remove_duplicates(list)
-  raise NotImplementedError, "Not implemented yet"
+  index = 0
+  while index <= list.length
+    if list[index] == list[index + 1]
+      list.delete_at(index)
+    end
+    index += 1
+  end
+  return list
 end
 
-# Time Complexity: ?
-# Space Complexity: ?
+
+
+# Time Complexity: O(n * m)
+# Space Complexity: O(1)
+
 def longest_prefix(strings)
-  raise NotImplementedError, "Not implemented yet"
+  prefix = strings[0]
+  original = prefix
+  a_length = strings.length
+  a_length -= 1
+  
+  
+  a_length.times do |index|
+    comparison_word = strings[index + 1]
+    w_length = prefix.length
+    w_length.times do |i|
+      if prefix[i] != comparison_word[i] 
+        i -= 1
+        prefix = prefix[0..i]
+        if prefix == original
+          return ""
+        end
+        break
+      end
+    end
+  end
+  return prefix
 end
 
+
+