CSC 207.01 2019S, Class 31: Binary search trees II

Overview

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

Preliminaries

News / Etc.

• Today we continue our exploration of binary search trees, focusing primarily on how we remove elements.
  • Continue partners from Wednesday.
• New policy If your code is not formatted according to Google style guidelines, neither the mentor nor I will help you.
• Do not use ArrayLists to implement queues. That turns dequeue into an O(n) algorithm. I’ve provied a simple queue implementation that should suffice.

Upcoming work

• Reading for Monday: chapter 12 of Osera
• Assignment 8 due Thursday the 25th
  • Your partner is your partner from today’s lab.
  • If you worked alone, find a partner.
• Lab writeup for today: TBD

Extra credit

Extra credit (Academic/Artistic)

• Dartanyan Brown discussion, 4pm Wednesday April 24, HSSC S3325
• Dartanyan Brown concert, 7:30 pm Wednesday April 24, Sebring-Lewis
• New: PBK Convo, Thursday, 11am

Extra credit (Peer)

• True West, downtown Community Arts Theatre, Friday, Saturday, Sunday (sold out, but you could be on the waiting list)
• Track and Field home on Saturday.

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)

• Participate in Kinetic Sculpture Competition: Saturday the 27th
  • https://bit.ly/kineticsculpture19
  • You’ll need to build your sculpture in advance
  • You get reimbursed for up to $200 in supplies, but must present to be reimbursed.
• Public speaking workshop - April 22 at 7pm in HSSC S3325, with Kathy Clemons-Beasley ‘05.

Other good things

• New ISO Cultural Show, Saturday 7:00-9:00, Harris Gym

Friday PSA

• Hopefully your weekend goes better than the start of class.

Questions

Skip lists

Linked list, with values in order (using comparator).

Nodes have multiple next links, depending on their “height”

Approximately 1/2 have only one next link

Approximately 1/2 of the remaining ones have only two next links

If the heights are relatively evenly distributed, this should be a log2 n algorithm.

Lab

Question: Do we need a special case for the leaf in remove?

    if (node.left == null) && (node.right == null) {
      return null;
    } else if (node.left == null) {
      return node.right;
    } else if (node.right == null) {
      return node.left;
    } else {
      ...
    } //

Note: BSTs will be on the exam. Make sure to save your code and share it with your partner.