diff --git a/lib/practice_exercises.rb b/lib/practice_exercises.rb
index 291e4e6..b740955 100644
--- a/lib/practice_exercises.rb
+++ b/lib/practice_exercises.rb
@@ -1,13 +1,36 @@
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n), linear,  because the amount of times the while loop iterates is directly proportionate to the length of the array.
+# Space Complexity: O(1), constant, because there is no additional data being stored in addition to the array that is passed through, the reference itself is being changed. 
 def remove_duplicates(list)
-  raise NotImplementedError, "Not implemented yet"
+  i = 0
+  
+  while i < list.length
+    if list[i] == list[i+1]
+      list.delete_at(i)
+    else 
+      i+=1
+    end
+  end
+  
+  return list
 end
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n*m), quadratic, because there are two loops present: the while and the each. Each of those loops are based on different data sizes, and are proportionate to the size of the data.  
+# Space Complexity: O(n), linear, because longest_prefix is a variable that may increase if the data size increases. 
 def longest_prefix(strings)
-  raise NotImplementedError, "Not implemented yet"
+  longest_prefix = ""
+  base_word = strings.min_by {|word| word.length}
+  i = 0
+  
+  while i < base_word.length
+    letter_to_match = base_word[i]
+    
+    strings.each do |word|
+      if word[i] != letter_to_match
+        return longest_prefix
+      end
+    end
+    longest_prefix += base_word[i]
+    i+=1
+  end
 end
-