Recitation 4
http://goo.gl/YN1BQ7
James Wei
Professor Peck
1/31/2014
Big-Oh
Big-Oh
Common APT
• Go to the course APT page and read the
prompt for the Common APT.
• In Eclipse, write code to solve this APT. Use
the tester as always to verify that your solution
works.
• Feel free to work with a friend.
• Ask the TAs if you have any questions!
Common APT
• There are many different ways to solve this
APT.
• What are some different solutions for
Common?
• How do these different solutions perform
(think Big O)?
List Manipulation
• If you haven’t already, snarf the code for
Recitation 4.
• Run the code for “fruit1.txt” and take note of
the output and what the code is doing.
• Try running the code for “fruit2.txt”.
• Why doesn’t this code work? Consider:
• What do the words that fail to be removed have in
common?
• How is the iteration index changing with each
iteration?
List Manipulation
• Let’s fix the code. One way we can do that is by
creating a new ArrayList and copying elements over
into that new list.
• Take some time to fix the code in Eclipse by writing a
new method called removeFromListGood().
• This method should create a new ArrayList, copy over
the elements we want to keep from the old list to the
new one, then update the old list to be equal to the new
list.
• Consider:
•
•
How do we make sure we are creating a new list instead
of a reference to the existing one?
How do we update the old list once we have finished
making the new list?
List Manipulation
• How else can we fix the broken list remove code?
• We can try manipulating the index as we loop
through the list.
• Create a new method called
removeFromListIndex() that does this. As you
code, consider:
•
•
•
What is the index at the end of each iteration?
What should the index be at the end of each iteration?
When should the index be manipulated before the
next iteration begins?
Have a good weekend!
Don’t forget to submit your answers!