# CS/ECE 374 fa22: Homework and Exam Policies

The course staff must critically examine close to ten thousand pages of homework submissions this semester! We desperately need your help to make sure homeworks are graded and returned quickly. If you have any questions or concerns about these policies, please don't hesitate to ask in lecture, during office hours, or on Piazza.

I apologize in advance for the length of this document. Most of this stuff is obvious to almost everybody, but after teaching this class for many years, I've seen a lot of strange things.

### Homework Logistics: How to submit

• Weekly homework would be made of three problems. One of them on PL, and two of them on submission on gradescope.
• Overall, there would be 33 homework problems.
• Every week one homework problem would be due on PrairieLearn (PL) on Tuesday morning.
• Each student has to do the PL problem on their own (i.e., no groups).
• All other homework problems solutions must be submitted electronically via Gradescope. Submit one PDF file for each numbered homework problem. Gradescope will not accept other file formats such as plain text, HTML, LaTeX source, or Microsoft Word (.doc or .docx).
• Homework solutions may be submitted by groups of at most three students. We strongly encourage (but will not require) every student to work in a group with at least one other student. Students are are responsible for forming their own homework groups. Groups may be different for each numbered homework problem.
• For group solutions, exactly one member of each group submits the solution to each problem. Even if the groups are identical, the submitter may be different for each numbered homework problem.
• Whoever submits any group solution must also submit the names of the other group members via Gradescope. Gradescope will then automatically apply the grade for that submission to all group members. If this information is not entered correctly, the other group members' grades will be delayed or possibly lost entirely.
• If you discover that your name was omitted from a group homework submission, please submit a regrade request.
• As error correction, each submitted homework solution should include the following information in large friendly letters at the top of the first page.
• The homework number
• The problem number
For group solutions, include the Gradescope name and email address of every group member. If you are typesetting your solutions with LaTeX, please use our solution template.
• If you must submit scanned handwritten solutions, use a black pen on blank white paper and a high-quality scanner app (or an actual scanner, not just a phone camera).
• We will not accept late homework for any reason. To offset this rather draconian policy, we will count only the top 26 homework problem toward your final course grade. Specifically:
• If you submit more than 26 homework problems, only your highest 26 problem scores count. (If you submit everything, this this is equivalent to dropping almost two complete homework sets.)
• If you submit fewer than 26 homework problems, then the homeworks not submitted are considered to have grade 0.
• You must submit at least 16 homework problems to pass the class.

### Form: How to write

Please make it easy for the graders to figure out what you mean in the short time they have to grade your solution. If your solutions are difficult to read or understand, you will lose points.

#### Be Clear

• Write legibly. If we can't read your solution, we can't give you credit for it. If you have sloppy handwriting, use LaTeX. Please don't submit your first draft. Writing legibly also helps you think more clearly.
• We strongly recommend typesetting your homework using LaTeX. (In particular, we recommend TeXShop for Mac OS X, TeX Live for Linux (already included in most distributions), and MiKTeX for Windows.) We will provide a LaTeX template for homework solutions.
• You are welcome to submit scans of hand-written homework solutions, but please write clearly using a black pen on plain white unlined paper, and please use a high-quality scanning app (or an actual high-quality scanner). We recommend printing your scanned document to check for readability before submitting.
• Write sensibly. You will lose points for poor spelling, grammar, punctuation, arithmetic, algebra, logic, and so on. This rule is especially important for students whose first language is not English. Writing sensibly also helps you think sensibly.
• Write carefully. We can only grade what you actually write, not what you mean. We will not attempt to read your mind. If your answer is ambiguous, the graders are explicitly isntructed to choose an interpretation that makes it wrong. Writing carefully also helps you think carefully.
• Avoid the Three Deadly Sins. Yes, we are completely serious about these. We reserve the right to add more Deadly Sins later in the course.
1. Write solutions, not examples. Don't describe algorithms by showing the first two or three iterations and then writing "and so on". Similarly, don't try to prove something by demonstrating it for a few small examples and then writing “do the same thing for all $n$”. Any solution that includes phrases like “and so on”, “etc.”, “do this for all $n$”, or “repeat this process” automatically gets a score of zero. Those phrases indicate precisely where you should have used iteration, recursion, or induction but didn’t.
2. Declare all your variables. Whenever you use a new variable or non-standard symbol for the first time, you must specify both its type and its meaning, in English. Similarly, when you describe any algorithm, you must first describe in English precisely what the algorithm is supposed to do (not just how it works). Any solution that contains undeclared variables automatically gets a score of zero, unless it is otherwise perfect. This rule is especially important for dynamic programming problems.
3. Never use weak induction! Always, always, always use a strong induction hypothesis, even in proofs that only apply the induction hypothesis at $n-1$. Why would you even want to tie $n-2$ hands behind your back? Any proof that uses a weak induction hypothesis automatically gets a score of zero, unless it is otherwise perfect. Basically, weak induction should die in a fire.
• State your assumptions. If a problem statement is ambiguous, explicitly state any additional assumptions that your solution requires. (Please also ask for clarification in class, in office hours, or on Piazza!) For example, if the performance of your algorithm depends on how the input is represented, tell us exactly what representation you require.
• Don't submit code. Describe your algorithms using clean, human-readable pseudocode. Your description should allow a bright student in CS 225 to easily implement your algorithm in their favorite language.
• Don't submit your first draft. Revise, revise, revise. After you figure out the solution, then think about the right way to present it, and only then start writing what you plan to submit. Yes, even on exams; do your initial scratch work on the back of the page.

#### Be Concise

• Keep it short. Every homework problem can be answered completely in at most two typeset pages or five handwritten pages; most problems require considerably less. Yes, I am aware of the crushing irony.
• Omit irrelevant details. Don't write "red-black tree" when you mean "balanced binary tree" or "dictionary". Don't submit code; We want to see your ideas, not syntactic sugar. If your solution requires more than two typeset pages, you are providing too many irrelevant details.
• Don't regurgitate. Don't explain binary search; just write "binary search". Don't write the pseudocode for Dijkstra's algorithm; just write "Disjktra's algorithm". If the solution appears on page 6 of Jeff's notes, just write "See page 6 of Jeff's notes." If your answer is similar to something we've seen in class, just say so and (carefully!) describe your changes. You will lose points for vomiting.
• Autmatic zero: We will give an automatic zero to answers which we consider to be too long, unclear, and repetitious. We will also do it if we can not follow the logic of your answer. We might even do it without reading them.

### Content: What to write

• Answer the right question. No matter how clear and polished your solution is, it's worthless if it doesn't answer the question we asked. Make sure you understand the question before you start thinking about how to answer it. If something is unclear, ask for clarification! This is especially important on exams.
• Justify your answers. You must provide a brief justification for your solutions, as evidence that you understand why they are correct. Unless we explicitly say otherwise, we generally do not want a complete proof of correctness—because complete proofs would be too long, tedious, and unenlightening—but rather a high-level sketch of the major steps in the proof. Proofs/justifications are only required on exams if we specifically ask for them.
• By default, if a homework or exam problem asks you to describe an algorithm, you need to do several things to get full credit:
• If necessary, formally restate the problem in terms of combinatorial objects such as sets, sequences, lists, graphs, or trees. In other words, tell us what the problem is really asking for. This is often the hardest part of designing an algorithm.
• Give a concise pseudocode description of your algorithm. Don't regurgitate, and don't turn in code!
• Describe a correct algorithm.
• Justify the correctness of your algorithm. You usually won't have to do this on exams.
• Analyze your algorithm's running time. This may be as simple as saying "There are two nested loops from 1 to n, so the running time is O(n²)." Or it may require setting up and solving a recurrence, in which case you'll also have to justify your solution.
• Describe the fastest correct algorithm you can, even if the problem does not include the words "fast" or "efficient". Faster algorithms are worth more points; brute force is usually not worth much. We will not always tell you what time bound to shoot for; that's part of what you're trying to learn. However, if your algorithm is incorrect, you won't get any points, no matter how fast it is!
Some problems may deviate from these default requirements. For example, we may ask you for an algorithm that uses a particular approach, even though another approach may be more efficient. (Answer the right question!)

## No IDK points

In the past, we used to give IDK (I dont know) points. We will not do this semester as it seems to discriminate against people that know what they are doing, but are not sure about it. Naturally, if you write IDK and save us time in grading, we might give you a point for saving us time, if we feel generous.

IDK points make sense when one enforces an aggressive policies of giving zero for solutions that are not very close to being correct. Naturally, students hate such aggressive grading policies.