EBoard 37: Heaps and heapsort, continued

Warning This class is being recorded (and transcribed) (assuming Teams succeeds).

Approximate overview

• Administrivia
• Questions
• Lab

Administrivia

• I hope you had a great Turkey break.
• I missed many of you last Wednesday. Very few of you who missed class notified me that you were going to miss class, in spite of the policy that you are supposed to do so.
• Prof. Jimenez and I bought you presents. The official class pen.

Upcoming Token activities

Academic

• Tuesday, 2023-11-28, Noon, Day PDR, CS Table: TBD.

Cultural

• Thursday, 2023-11-30, 11am, JRC 101: Let’s talk institutional memory.

Peer

• Friday, 2023-12-01, 5:30pm, Natatorium: Swimming (Pioneer Classic)
• Friday, 2023-12-01, 5:00pm, Field House: Indoor track and field
• Saturday, 2023-12-02, all day, Natatorium: _Swimming (Pioneer Classic)

Wellness

We need more of these!

Misc

• Subject yourself to a study of types.
• Please fill in the peer educator evaluations

Other good things (no tokens)

Upcoming work

• Reading for Wednesday: CLRS B.4.
• Thursday: Mini-project 9

Questions

Heaps

MP9

Administrative

I forgot to fill in the pre-assessment for mini-project 9 even though I knew that I had to do so to make up for the prior missing pre-assessments and you reminded us to do so. Could I please turn it in today?

Sure.

Lab

Should we create a min-heap or a max-heap?

Please create a min-heap.

Does it matter if I write heapUp iteratively or recursively?

Nope. I think it’s easier to write recursively, but I ended up writing it iteratively when I did the lab.

Does it matter if I write heapDown iteratively or recursively?

Nope. I think it’s easier to write recursively, and I ended up writing it recursively when I did the lab.

Do you have hints on heapDown?

Strategy one: Write a helper procedure that returns the index of the smaller child. You can then compare i to that index. (Make sure that you check whether there is a right child.)

Strategy two: Keep track of the index of the smallest element seen so far. Initially, that’s i. If you have a left child and the left child is smaller, you can update that index. If you have a right child and the right child is smaller, you can update that index. Once you’re done, you can compare that index to i. If they are different, swap and recurse (recur). (I think CLRS use this strtegy.)