I am enrolled in the 2015 offering of the course on edX. I have already submitted Pset 0. I am trying to submit Pset 1 after listening to the Week 1 lessons. When I select courseware, then week 1, the Pset available there is Pset 0. And now there is no Pset 0 under Week 0. Under Week 2, there is Pset 1 and so on.

Why don't the problem set numbers correspond to the week numbers?

  • That is normal, on campus problem sets are due the following week. Commented Jan 9, 2015 at 15:35

3 Answers 3


This was a source of confusion during last year's offering of the course too. Professor Malan addressed this in a comment on Reddit.

On campus, students tend to work on Problem Set 0 during Week 1, which is why we had it in Week 1 earlier.

Since there was so much confusion about it last year, they eventually moved the problem sets so that their numbers corresponded with the numbers of the week.

We've indeed relocated Problem Set 0 to the bottom of Week 0 for clarity (and Problem Set 1 to the bottom of Week 1).

But while this alleviated the confusion, it caused a new problem. The week 2 lectures, for instance, usually contained further discussion and exposition directly related to problem set 1, because the campus students had still been working on problem set 1 during week 2. Some Edx students missed out on these additional discussions when the problem sets were shifted to an earlier week. Therefore they had more difficulties solving the problems. I suspect that is the reason why they've reverted back to the original arrangement this year.

  • 2
    Prof Malan told me yesterday that he was making the move for the very reasons stated above. If it causes a lot more confusion, then it may be switched back, as it was last year. But for now, the psets are placed in the week in which they were due (in the in-person class).
    – curiouskiwi
    Commented Jan 10, 2015 at 8:27
  • Thank you guys for clearing up my mind. Now it makes sense. Commented Jan 10, 2015 at 16:55
  • @curiouskiwi Thanks for the confirmation!
    – Chrisuu
    Commented Jan 10, 2015 at 22:51
  • @NataliaGligor You can also accept this answer by clicking the checkmark next to it.
    – Chrisuu
    Commented Jan 10, 2015 at 22:52

Seems that for some reason, all psets on edX CS50 shifted one week upwards.

However, there is no official notice so far on whether it was intentional or what was the reasoning for it (fewer psets? or more psets towards the end?)

  • An official note from the staff about the reasoning behind this arrangement was posted to Reddit last year. This answer has additional details and a link to the original discussion.
    – Chrisuu
    Commented Jan 9, 2015 at 18:52

I thought there was a problem with it too, but I was wrong. Go to your CS50 courseware and take a look at Problem Set 0. Link

Don't forget to do these things before submitting :

Your project must have at least two sprites, at least one of which must resemble something other than a cat.

Your project must have at least three scripts total (i.e., not necessarily three per sprite).

Your project must use at least one condition, one loop, and one variable.

Your project must use at least one sound.

Your project should be more complex than most of those demonstrated in lecture (many of which, though instructive, were quite

short) but it can be less complex than, say, Pikachu’s Pastry Catch and Ivy’s Hardest Game. As such, your project should probably use a few dozen puzzle pieces overall.

Once finished with your project, click See project page in Scratch’s top-right corner. Ensure your project has a title (in Scratch’s top-left corner), some instructions (in Scratch’s top-right corner), and some notes and/or credits (in Scratch’s bottom-right corner). Then click Share in Scratch’s top-right corner so that others (e.g., your TF!) can see your project. Finally, take note of the URL in your browser’s address bar. That’s your project’s URL on MIT’s website, and you’ll need to know it later.

At the end of the page, you'll find a part How To Submit Here's what it says :

To submit this problem set, visit http://cs50.edx.org/2015/psets/0/. You’ll find that a few questions await. Be extra-sure that your answers are correct, particularly your project’s URL on MIT’s website, lest we overlook your submission!

CS50 collects quite a bit of data for research purposes. Please forgive the length of this first problem set’s form! In total, the form will probably take 30 or more minutes to fill out. Not to worry if you finish shortly after the problem set’s deadline, so long as you start before the deadline. Future problem sets' forms will be much quicker!

  • The author has already submitted problem set 0. She is asking why the problem set n is posted under week n + 1 on Edx.
    – Chrisuu
    Commented Jan 9, 2015 at 18:11
  • I indeed submitted pset0, no questions regarding that. Now everything is clear. Thank you everyone for your help. Commented Jan 10, 2015 at 16:56

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