CSC 207.02 2019S, Class 26: Array-based lists

Overview

• Preliminaries
  • Notes and news
  • Upcoming work
  • Extra credit
  • Questions
• Lab
• Debrief

Preliminaries

News / Etc.

• If you would like my programs from Friday and promise not to distribute them to others, I can send them to you. (I need an email from you indicating that you promise not to distribute them to others.)
• I am a bit puzzled by the disconnect between “I had difficulty with Big O” and attendance at last night’s mentor session.

Upcoming work

• Readings for Wednesday
  • Iterating lists
  • Doubly and circularly linked lists
• Makeup exam 1 due Thursday the 11th
  • You can bring your printed version to class on Friday
• Lab writeup: Exercise 6b

Extra credit

Extra credit (Academic/Artistic)

• CS Table Tomorrow - The Autocrat’s New Toolkit

Extra credit (Peer)

Extra credit (Wellness)

Extra credit (Wellness, Regular)

• 30 Minutes of Mindfulness at SHACS/SHAW every Monday 4:15-4:45
• Any organized exercise. (See previous eboards for a list.)
• 60 minutes of some solitary self-care activities that are unrelated to academics or work. Your email reflection must explain how the activity contributed to your wellness.
• 60 minutes of some shared self-care activity with friends. Your email reflection must explain how the activity contributed to your wellness.

Extra credit (Misc)

• “State of SHAW” talk Thursday at 11am in JRC 101.
  • When did SHACS get renamed?
• Participate in Kinetic Sculpture Competition: Saturday the 27th
  • You’ll need to build your sculpture in advance
  • https://bit.ly/kineticsculpture19
• Wednesday the 10 at 4pm on Mac Field: Giant Laurel Leaf. (Free t-shirt!)
• Scarlet and Give Back Day next Wednesday/Thursday (I think). If you don’t have money to donate, let me know and I will give you $5 to donate on Monday.
• Prosp a Hostie

Other good things

Questions

Do we need comparators for QuicksortDNF?

No. You’re only dealing with arrays of integers.

Did I ask that before?

Probably. But I forgot to put it in the eboard.

Can’t we write our own comparator for integers?

Yes. But you shouldn’t use it in problem 2.

What’s the difference between an iterator and a cursor?

Both are used for iterating lists.

Cursor, in my world, is a movable position. You can look at the cursor. You can advance it. You can retreat it.

Iterator, in Java, supports similar operations, but you move the iterator each time you ask for an element.

Lab

Setting/removing at the end

How might you end up with the following state?

A B C
     ^

Option 1: Start with the list [A,B,C]. Make an iterator. Call next(), next(), next(). (It is legal to call set or remove.)

Option 2: Start with the list [A,B,C]. Make an iterator. Call next(), next(), add(D). (It is not legal to call set or remove.)

Option 3: Start with the list [A,B,C,D]. Make an iterator. Call next(), next(), next(), next(), remove(). (It is not legal to then call set or remove.)

Setting in bi-directional lists

When implementing set with previous, you may find it useful to have a variable that keeps track of the index of the element to set or remove. (Set it to something like -1 or Int.MIN_VALUE if you can’t set or remove.)

Writeup

Writeup: Exercise 6b

This is class 26.

Debrief

Moral: Adding and removing elements is likely to be expensive if the underlying structure is an array. So be careful about using ArrayLists when you need an expandable list.