diff --git a/lib/practice_exercises.rb b/lib/practice_exercises.rb
index 291e4e6..9fcef1f 100644
--- a/lib/practice_exercises.rb
+++ b/lib/practice_exercises.rb
@@ -1,13 +1,47 @@
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: 0(1)
 def remove_duplicates(list)
-  raise NotImplementedError, "Not implemented yet"
+  i = 0
+  j = 1
+  until list[j] == nil
+    if list[i] == list[j]
+      list.delete_at(list[j])
+    else
+      i+=1
+      j+=1
+    end
+  end
+  return list
 end
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n^4)
+# Space Complexity: 0(n)
 def longest_prefix(strings)
-  raise NotImplementedError, "Not implemented yet"
+  i = 1
+  j = 0
+  k = 0
+  output = ""
+  characters = []
+  length = strings.length
+  strings.each do |word|
+    characters << word.chars
+  end
+  
+  characters.each do |item|
+    until j == length-1
+      until k == length-1
+        if item[k] != characters[i][k]
+          return output
+        else
+          
+          i += 1
+        end
+        output += item[k]
+        k += 1
+        j += 1
+      end
+    end
+    return output
+  end
 end
-