Eboard 27: Linked Lists

You are being recorded and transcribed.

Please sit with your MP7 partner.

Approximate overview

• Administrivia
• Lab

Preliminaries

• Thanks to whoever told our mentor to tell me that I’m not giving you enough time for lab.
  • Note that Wednesday was intentionally a “let’s figure out list iterators” day (based on my experiences last semester). We’ll still have time for that lab on Monday.
• Note: Class is “virtual” on Monday. You should do the lab on your own (with or without a partner), checking in with me if/when you need help.
• We understand lists best when we diagram them. Consider grabbing a whiteboard and marker.

Upcoming work

Schedule needs updating. Stay tuned.

• Friday, 2024-04-05, MP6 post-assessment
  • Submit MP6 post-assessment on Gradescope
• Friday, MP7 pre-assessment
  • Individual
  • Submit MP7 pre-assessment on Gradescope
• Wednesday, MP7
  • Group
  • Submit MP7 on Gradescope
• Sunday, 2024-04-14, MP3 redo
  • Submit MP3 redo on Gradescope
• Sunday, 2024-04-14, MP4 redo
  • Submit MP4 redo on Gradescope

Tokens

Academic/Scholarly

• Tuesday, 2024-04-09, noon, Some PDR. CS Table.
• Tuesday, 2024-04-09, 7:00pm, Science 3819. Mentor Session.
• Thursday, 2024-04-11, 4pm, HSSC 1231 (the Kernel). CS Poster Session.

Cultural

• Friday, 2024-04-05, 4pm, Global Living Room in HSSC. Middle of Everywhere.
• Saturday, 2024-04-06, 1–4pm, Cleveland Beach (in front of Cleveland residence hall on South Campus). Holi. Beware, your clothes will get stained.
  • Follow the instagram page for info. @umwhatiscalledshibam [no]. @shibamquick [no]. @saso_grinnell [maybe]
• Saturday, 2024-04-06, 7:00-8:00pm, Global Living Room. Eid extravaganza.
• Sunday, 2024-04-07, 1:00-4:30pm, Harris. Purim Carnival.
• Sunday, 2024-04-07, 2:00-3:30pm, Sebring-Lewis. Eugene Gaub Recital.
• Thursday, 2024-04-11, 4:15-5:30pm, HSSC S1325 Writers@Grinnell.
• Thursday, 2024-04-11, 8:00-9:30pm, JRC 101 Writers@Grinnell.
• Friday, 2024-04-12, 4:00-5:00pm, HSSC N1170 Middle of Everywhere.
• Saturday, 2024-04-13, ??? (@nepali_grinnellians on instagram for more info)

Peer

• Saturday, 2024-04-06, 9am–noon, Field House (?) Men’s Tennis vs. Illinois College.
• Saturday, 2024-04-06, 3pm–6pm, Field House (?) Men’s Tennis vs. Monmouth.

Wellness

• Tuesday, 2024-04-09, noon-1pm, BRAC P103. HIIT and Strength Fitness Class.
• Tuesday, 2024-04-09, 12:15–12:50, Bucksbaum 131. Yoga in the Museum.
• Tuesday, 2024-04-09, 4pm, BRAC P103 (Multipurpose Dance Studio): Yoga.
• Friday, 2024-04-12, 3:00–5:00pm, JRC Courtyard Get Nostalgic.

Misc

• Monday, 2024-04-08, 1:00–3:00pm (approx), where appropriate. Watch the eclipse (but don’t stare at the sun).
  • Eclipse glasses being given away at Burling (we think) and by the Physics SEPC (we know).

Other good things to do (no tokens)

Friday PSA

• You’re awesome. People care about you. (At least one person, as long as you consider me a person.) -> You have a responsibility to take care of yourself.
• Be moderate.
• Watch your drink container.
• Consent is essential (discussion is better).

Questions

Please avoid distracting questions.

Registration

Administrative

Lists

MP7

Other

Lab

Kudos

I appreciate how readily you talk to each other about design.

On lab design

At some times, it’s better to plan and read rather than just implement.

• You’ll likely miss everything the first time through; this makes you a bit more efficient.
• [But you knew that; it’s a theme of the labs in the course.]

Exploring remove

a. Why do we have the last two lines of remove?

  void remove() {
    if (this.prev != null) {
      this.prev.next = this.next;
    }
    if (this.next != null) {
      this.next.prev = this.prev;
    }
    this.prev = null;
    this.next = null;
  } // remove()

b. Where’s the call to free?

Interface vs. implementation

Even if we implement a List (abstract) as a CircularlyDoublyLinkedList (implementation), all of the operations should assume that it’s just a List. Hence, even though there’s a next node for the last node in the list, hasNext should return false.

Some morals (if there’s time)

• At times, Sam (or someone) writes beautifully weird code. E.g.,
  • removeExpt(stuff, (str) -> ((counter.get() % 2) == 0))
• We understand much better when we draw pictures [x3]
  • We can also trace code on paper.
  • It’s easy to get lost in lists unless you draw pictures.
• We understand cursors/iterators better. [+1]
• We should remember what we’ve done before; it helps.
• Take more notes while working.
• Iterators can be complex to learn.
• It’s hard to keep track of all the fields.
• It’s weird that we have two remove functions (one for the node and one for the iterator). But it makes sense (one is conceptual, one is implementation).
• There are a lot of nuances and special cases, at least if you make some design decisions.