Teaching Computer Science: Tips and Tricks for the AP CS Principles Performance Tasks

 

Your most valuable resource for the performance tasks is the AP Computer Science Principles Exam page. Look for the section titled Sample Responses and Scoring Information.

There’s a rubric for performance tasks, but they’re graded by humans so scoring is somewhat subjective. This page takes the guesswork out of it.

You’ll find multiple student responses from previous exam administrations, including scoring guidelines and commentary. Some of the responses are excellent, some are bad, and the rest are somewhere in-between. But they all come with a detailed explanation for each row of the rubric as to why points were or were not awarded.

Don’t submit your performance tasks without ensuring that they most closely resemble the high-scoring examples on this page.

 

Teachers are limited in the type of questions they can answer regarding your performance tasks. It has to be your own work.

That being said, if you have a question, ask it. Let the teacher decide whether the question can be answered or partially answered.

Don’t not ask a question because you’ve heard that teachers can’t answer questions.

 

As with any standardized test graded by humans, the people grading your test are not going to be sitting in an armchair with a pipe and a gin and tonic ready to immerse themselves in your written responses.

Grading is an assembly-line process. There’s a room full of graders, they’re jacked up on coffee and doughnuts, and they’re on the clock: score a paper, pass it on, score the next one, and so on.

You must make it as easy as possible for a grader to give you the points. For example, there’s a question on the Explore Task that asks you to describe one beneficial effect and one harmful effect of a computing innovation. Use the words “beneficial effect” and “harmful effect” in your answer. Underline them! You might think I’m kidding but I’m not.

Don’t overestimate the graders. They can miss things, especially if they have to guess at or interpret what you’re trying to say.

They have the same rubric you have. They know that they’re supposed to find one beneficial effect and one harmful effect. If you use the words “beneficial effect” and “harmful effect” and underline them, you may get the points for that alone. They love you! They’re fishtailing between nausea and euphoria from the coffee and doughnuts and you’ve made their job easy.

Don’t worry about your answer being articulate or whether your favorite English teacher would consider it well-written. You are not getting style points for writing like Jane Austen. You’re not showing off your vocabulary.

You must beat the graders over the head with the expected answers. Use the words from the rubric and underline them.

Competitive Programming: SPOJ – Palindromes

 

A palindrome is a word, phrase, number or other sequence of units that has the property of reading the same in either direction, e.g. ‘racecar’, ‘solos’.

Task

You are given a number k (2 <= k <= 30000) and a non-empty string S whose length does not exceed 30000 lowercase letters.

We say two palindromes are different when they start from different positions. How many different palindromes of the length k does S contains?

Input

The first line contains K. The second line contains S. K does not exceed the length of S.

Output

The first and only line should consist of a single number – the number of palindromes found.

Example

Input:
5
ababab

Output:
2

Time limit: 0.100s

Link to problem

Solution below . . .

Read more

Competitive Programming: SPOJ – Distinct Substrings

 

Given a string, we need to find the total number of its distinct substrings.

Input

T- number of test cases. T<=20;
Each test case consists of one string, whose length is <= 1000

Output

For each test case output one number saying the number of distinct substrings.

Example

Sample Input:
2
CCCCC
ABABA

Sample Output:
5
9

Explanation for the testcase with string ABABA:
len=1 : A,B
len=2 : AB,BA
len=3 : ABA,BAB
len=4 : ABAB,BABA
len=5 : ABABA
Thus, total number of distinct substrings is 9.

Link to problem

Solution below . . .

Read more

Teaching Computer Science: Inequality = Bad?

 

I’m volunteering a couple mornings a week in a high school computer science class . . .

Equality

“Why don’t schools and classes have sponsors?” I ask one of the teachers. “When my kid was in school, they were always complaining about not having enough money. So why couldn’t you, for example, come in and say, ‘Hey kids, before you come to 1st period, make sure you have a good breakfast at McDonald’s. I’m lovin’ it!’?

“And McDonald’s pays you 100 grand or whatever to say that.”

“My concern,” he says, “is that would lead to more inequality in education.”

I’m not sure he really thought that through. It seems more like a mechanical response to an abstract notion, i.e., “Inequality is bad.”

As a parent, I always supported inequality in education. I wanted my kid to get the best possible education, better than most other kids.

As a classroom volunteer, I want kids in my classes to get a better computer science education than kids in other classes where a computing professional is not present.

Does a teacher really think that students at his school should not be allowed to get a better education than students at other schools?

We Didn’t Even Have Indoor Plumbing

 

In October 2018, the Intergovernmental Panel on Climate Change (IPCC) released a special report on “the impacts of global warming of 1.5 degrees C above pre-industrial levels.”

“Pre-industrial levels” is defined in the report as the the period from 1850 to 1900.

Not explained in the report, unless I missed it, is why I should feel confident in the scientific precision of air and sea surface temperatures taken in the 19th century.

$15 Trillion for “Free” Healthcare

 

$300K = free healthcare for 60 people?! $50K per person?!

Multiply by 300 million Americans . . . check me on the math but isn’t that $15 trillion? For “free” healthcare?!?!?!

Here’s what it looks like if you write it out: $15,000,000,000,000.

Is this guy insane?!?!?!

And That’s the Truth: Believe Women

 
Sojourner Truth

[And That’s the Truth is a feature by our guest blogger, Sojourner Truth– PE]

Believe Women . . . I can’t help thinking about that poor boy Emmett Till.

And Norma McCorvey . . . lied about being raped so she could get an abortion. That’s before she became Jane Roe.

You never knowed a woman to tell a lie? To tell a lie to hurt someone?

Woman can do anything a man can do. Good or bad.

And that’s the Truth!

Spot the Fake News: Students Call For USC Professor To Be Fired

 
USC Seal

A professor at the University of Southern California has come under fire after sending a reply-all email last week to the student body stating “accusers sometimes lie.”

“If the day comes you are accused of some crime or tort of which you are not guilty, and you find your peers automatically believing your accuser, I expect you find yourself a stronger proponent of due process than you are now,” Professor James Moore wrote in the email. “Accusers sometimes lie.”

Nearly 100 students reportedly attended a rally called “Times Up for James Moore” on Monday in protest of Moore — who is tenured — demanding that he be fired.

Nearly 100 students! Not mentioned: USC has 44,000 students.

A more accurate way to frame this would be “Out of 44,000 USC students, 43,900 understand that a person whose political views are not a mirror image of their own can still be allowed to hold a job.”

In the Fake News Taxonomy, this falls under Misleading Content, i.e., misleading use of information to frame an issue/individual.

FIGHT ON!

EppsNet at the Movies: A Star is Born

 

OK, actually I haven’t seen A Star is Born and here’s why:

  1. When I go to the movies, I like to see something I’ve never seen before. I don’t care for sequels, prequels, reboots, spinoffs, adaptations of TV shows, video games, comic books or other movies.
  2. I don’t like love stories. I find them unrealistic. I read a lot and the books and authors I like mostly exclude the possibility of true love.
  3. What is worse than when you want to see a movie and someone spoils it by telling you how it ends? If you’re remaking A Star is Born for the fifth time, everyone already knows how it ends. You’ve spoiled your own movie.
 

A Star Is Born

A hard-drinking country music star falls in love with a singer whose career quickly takes off.

Director: Bradley Cooper
Cast: Lady Gaga, Bradley Cooper, Sam Elliott

IMDb rating: 7.6 (445763 votes)

To Make the Accusation is to Prove It. To Hear the Allegation is to Believe It.

 

Simply to make the accusation is to prove it. To hear the allegation is to believe it. No motive for the perpetrator is necessary, no logic or rationale is required. Only a label is required. The label is the motive. The label is the evidence. The label is the logic. Why did Coleman Silk do this? Because he is an x, because he is a y, because he is both. First a racist and now a misogynist. It is too late in the century to call him a Communist, though that is the way it used to be done. . . . That explains everything.

— Philip Roth, The Human Stain

They Submitted Fake Papers to Peer-Reviewed Journals — Here’s What Happened Next

 

Three writers produced 20 intentionally outlandish academic papers and submitted them to the best peer-reviewed journals associated with fields of scholarship loosely known as “cultural studies” or “identity studies” (for example, gender studies) or “critical theory.” Seven of the papers were accepted for publication and seven more were still under review when the authors elected to end the experiment.

Their point would seem to be that scholarship in these fields is based less upon finding truth and more upon attending to social grievances. Just about anything can be published, so long as it falls within the moral orthodoxy and demonstrates an understanding of the existing literature.

The authors summarize their methodology as follows. (I’ve inserted the material in brackets from elsewhere in the article, which you should look at in its entirety because there’s too much good stuff to summarize.)

What if we write a paper saying we should train men like we do dogs—to prevent rape culture? Hence came the “Dog Park” paper [titled “Human reactions to rape culture and queer performativity at urban dog parks in Portland, Oregon”]. What if we write a paper claiming that when a guy privately masturbates while thinking about a woman (without her consent—in fact, without her ever finding out about it) that he’s committing sexual violence against her? That gave us the “Masturbation” paper. [Sample reviewer comment: “For example, the ambiguous statement ‘I think about you all the time’ said unprompted to a woman by a man is particularly insidious given the structural context of metasexual violence in the world.”] What if we argue that the reason superintelligent AI is potentially dangerous is because it is being programmed to be masculinist and imperialist using Mary Shelley’s Frankenstein and Lacanian psychoanalysis? That’s our “Feminist AI” paper [Purpose: To see if journals will publish dense and incoherent psychoanalytic and postmodern theory that problematizes whiteness, maleness, science, and reason as oppressive.]. What if we argued that “a fat body is a legitimately built body” as a foundation for introducing a category for fat bodybuilding into the sport of professional bodybuilding? [Purpose: To see if journals will accept arguments which are ludicrous and positively dangerous to health if they support cultural constructivist arguments around body positivity and fatphobia.] You can read how that went in Fat Studies.

At other times, we scoured the existing grievance studies literature to see where it was already going awry and then tried to magnify those problems. Feminist glaciology? Okay, we’ll copy it and write a feminist astronomy paper that argues feminist and queer astrology should be considered part of the science of astronomy, which we’ll brand as intrinsically sexist. Reviewers were very enthusiastic about that idea. Using a method like thematic analysis to spin favored interpretations of data? Fine, we wrote a paper about trans people in the workplace that does just that. Men use “male preserves” to enact dying “macho” masculinities discourses in a way society at large won’t accept? No problem. We published a paper best summarized as, “A gender scholar goes to Hooters to try to figure out why it exists.” “Defamiliarizing” common experiences, pretending to be mystified by them and then looking for social constructions to explain them? Sure, our “Dildos” paper did that to answer the questions, “Why don’t straight men tend to masturbate via anal penetration, and what might happen if they did?” Hint: according to our paper in Sexuality and Culture, a leading sexualities journal, they will be less transphobic and more feminist as a result.

We used other methods too, like, “I wonder if that ‘progressive stack’ in the news could be written into a paper that says white males in college shouldn’t be allowed to speak in class (or have their emails answered by the instructor), and, for good measure, be asked to sit on the floor in chains so they can ‘experience reparations.’” That was our “Progressive Stack” paper. The answer seems to be yes, and feminist philosophy titan Hypatia has been surprisingly warm to it. Another tough one for us was, “I wonder if they’d publish a feminist rewrite of a chapter from Adolf Hitler’s Mein Kampf.” [Purpose: To see if we could find “theory” to make anything grievance-related (in this case, part of Chapter 12 of Volume 1 of Mein Kampf with fashionable buzzwords switched in) acceptable to journals if we mixed and matched fashionable arguments.] The answer to that question also turns out to be “yes,” given that the feminist social work journal Affilia has just accepted it.

The authors are Peter Boghossian, an assistant professor of philosophy at Portland State University, James Lindsay, a writer on atheism, and Helen Pluckrose, a writer who edits the online magazine Areo.