CSC 151.01, Class 39: Merge Sort

Overview

• Preliminaries
  • Notes and news
  • Upcoming work
  • Extra credit
  • Notes on exam 4
  • Questions
• Lab
• Debrief

News / Etc.

• I hope to have tentative project grades to you by Monday (ignoring the presentation component).
• We will discuss the form of the final Monday.
• I will have all your grades to you Monday of finals week.

Upcoming work

• Writeup for class 38 due TONIGHT at 10:30 p.m.
  • Exercise 5.
  • To: csc151-01-grader@grinnell.edu
  • Subject: CSC 151.01 Writeup 38 (YOUR NAMES)
• Writeup for class 39 due Monday at 10:30 p.m.
  • Exercises 4f, 4g, and 4h
  • To: csc151-01-grader@grinnell.edu
  • Subject: CSC 151.01 Writeup 39 (YOUR NAMES)
• Exam 4
  • Prologue due TONIGHT
  • Exam due Tuesday
  • Cover sheets due Wednesday
  • Epilogues due Wednesday.
• No more readings.
• No more quizzes (after today).

Extra credit (Academic/Artistic)

• CS Extras Thursday: Summer opportunities in CS.

Extra credit (Peer)

• Jazz Ensemble Concert TONIGHT at 7:30 p.m.
• Chamber Ensembles Saturday at 4:00 p.m.

Extra credit (Misc)

• Mental Health Campus Resource Fair. Friday at 4pm in JRC 209.
• Newtown movie Tuesday night.
  • Whoops! If you see the movie, you can have an extra day on Exam 4.

Other good things

• Swim meet this weekend. (Friday at ???. Saturday at ???.)
• One acts this weekend.
• YGB concert Saturday at 2p.m.
• Collegium Concert Sunday at 2:00 p.m.
• Festival of trees Friday at Drake.

Notes on exam 4

I have responded to most of the prologues that I have received. Here are some common notes.

Problem 1

• You can’t just add counters or use the debugger, since many of the “expensive” procedures are built in.
• Hence, you’ll need to think about which procedures are “slow” (in that they look at the whole list).
• You may want to make a list of the procedures each calls and think about whether each is “fast” or “slow”.

Problem 2

• I’d recommend direct recursion without an accompanying “tally”.
• I’d recommend that you use pair? rather than list? to check whether something is a sublist. (We did say that the input was well formed.)

Problem 3

• No changing the vector.
• No using vector append.
• No using lists.

Problem 4

• Remember that you need to use binary search.
• “use binary search” means “use the approach” not “call the procedure”
• Do not change the vector.

Problem 5

• The hard part of the problem is part e.
• You need to write about this problem even if you decide not to do it.

Other

• The most common answer to Q3: “I’m going to do problem 6 because I enjoy whatzitdos and dislike trees.”
• The second most common answer: “I don’t really like whatzitdos, but I like trees even less.”

Questions

Quiz

Lab

Please refresh when you do problem 4.

Sorry about the typos. I keep forgetting that I renamed procedures this semester.

Writeup: 4fgh RELOAD BEFORE YOU DO THESE PROBLEMS!

Debrief

How many times is merge called in (merge '(1 2 3 4) '(5 6 7 8) <=)?

How many times is merge called in (merge '(1 3 5 7) '(2 4 6 8) <=)?

Why aren’t the numbers the same?