CS/ECE 374 Homework

Homeworks & Deadlines

All homeworks are due Monday at 11pm on Gradescope. We will post each week's homework on Tuesday. We might post it a day earlier if the homework is ready. However, some homework material might not be covered before Tuesday's lecture. Each homework is accompanied with one solved problem as an example. Homeworks can be done in groups of three. There are no late submissions what so ever. Read the below homework policies for more details!

If you plan to typeset your solutions, please use the following: LATEX solution template.

homework tex in case they help (use at own risk): [hw2] [hw3]

Homework Logistics: How to submit?

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.

  • All homework 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).
  • Please register with Gradescope using your illinois email ID so we can give you credit for your homework.
  • 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 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
    • Your GradeScope name
    • Your Gradescope email address
    For group solutions, include the Gradescope name and email address of every group member.
  • WE WILL NOT ACCEPT LATE HOMEWORK FOR ANY REASON.

    Gradescope will stop accepting submissions at 11 p.m. on the due date and we will not accept solutions that are emailed or delivered to us by another means, even if it is at 11:01 p.m. We strongly encourage you to submit some solution before 11 p.m. in case you have some technical difficulties uploading. You are always able to upload another version and we will grade the latest version uploaded.

    To make up for this strict policy, we will only count the best 24 problems that you submit (out of approximaely 30-33 that we will assign) in your grade. This is equivalent to dropping 2 or 3 complete homeswork sets. You must, however, submit at least 16 homework problems to pass the class. See Grading Policy for more details.

We may forgive coursework under extreme circumstances, such as documented illness or injury. Forgiving homework requires a serious long-term issue that prevents submission of multiple homework sets; the regular homework policies already allow missing a few submissions without any penalty. "Extreme circumstances" do not include travel for job interviews. We will compute your final course grade as if your forgiven work simply do not exist; your other work will have more weight.

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.

(1) Be Honest:
  • Write everything in your own words, and properly cite every outside source you use. We strongly encourge you to use any outside source at your disposal, provided you use your sources properly and give them proper credit. If you get an idea from an outside source, citing that source will not lower your grade. Failing to properly cite an outside source—thereby taking credit for ideas that are not your own—is plagiarism.

    The only sources that you are not required to cite are the official course materials (lectures, lecture notes, homework and exam solutions from this semester) and sources for prerequisite material (which we assume you already know by heart).

  • List everyone you worked with on each homework problem. Again, we strongly encourage you to work together, but you must give everyone proper credit. If you work in a group of 20 students, then all 20 names should appear on your homework solution. If someone was particularly helpful, describe their contribution. Be generous; if you're not sure whether someone should be included in your list of collaborators, include them. For discussions in class, in section, or in office hours, where collecting names is impractical, it's okay to write something like "discussions in class".
  • Please see our academic integrity policy for more details.
(2) 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 " 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.
(3) 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!)