# Feedback Key

## Problem Sets

To allow for more concise and consistent feedback on your homework, I use a small key to mark common comments. It is helpful to interpret these comments (and other feedback you get) in reference to the Rubric and Homework Guidelines, so please consult those too. If you'd like clarification of what I mean in a particular case, you're welcome to drop by office hours.

C
Please be more concise. This mark may also indicate extraneous text.
E
Please be more explicit here. The labeled work is insufficiently explicit / insufficiently precise.
FP
Potential false positive: your algorithm or proof may report an answer as correct when it is incorrect. This could mean that it could claim something is true or optimal when it is otherwise, or that it may do something when nothing should be done.
FN
Potential false negative: your algorithm or proof may miss a correct answer when it exists. This could mean that it could claim something is false or not optimal when it is otherwise, or that it may fail to do something when it should.
G
Your work needs to be more general here. Perhaps you only considered a special case?
L
Be lazy. It's possible to write this algorithm or proof more clearly, concisely, and convincingly by referring to a pre-existing algorithm we covered in class.
M
Use formal mathematical notation here, and/or express what you mean in mathematical terms.
RC
You make repeated calls to a helper algorithm/subroutine, but it's not clear how the input differs on each call. If you call the same algorithm on the same input, you get the same output.
S
This does not match the problem specification.
T
Asymptotic running times (or spaces) should be reported without constant factors or lower-order terms. Terms for different parameters (like $f(x)$ and $g(y)$) should not be combined unless $f(x) = \Theta(g(y))$.
V
There is a problem here with your proof/argument; it is either invalid, not convincing, or insufficiently rigorous. This may be because there are holes in your logic, because your conclusions are not supported by your argument, because you have made a significant claim without proof, because you have failed to address an important possibility or case, or for some other reason.
W
You do unnecessary extra work in this algorithm, even though it doesn't significantly affect the asymptotic running time.
XP
The toolbox algorithm you used does not obviously have the extra properties / capabilities / outputs you claimed for it. Maybe there's a clever way to use or modify this algorithm so that it does what you said, but you didn't explicitly explain how.
?
This is unclear or confusing. Make your reasoning or instructions more clear or straightforward.
!?
This is needlessly complicated. Simpler approaches or arguments exist that are equally good, but easier to convey.

## Exams

Feedback on exams may use any of the symbols above, plus these ones that are more specific to issues on exams:

J
Though your answer may be fine, your justification has some issues.
!J
Your justification is incorrect.
P-
Not correct, but a correct conclusion from your previous (incorrect) answers.
P+
Correct, but an incorrect conclusion from your previous (incorrect) answers. Alternately, this may simply mean: “right answer, wrong reason”.
U
Answers should be unique: at most one answer may be submitted for a question. You either tried to submit multiple answers, or it wasn't clear enough what your answer was. Either way, you should indicate a single answer by putting a box around it.