Problem Set 4

Collaboration on problem sets is not permitted except to the extent that you may ask classmates and others for help so long as that help does not reduce to another doing your work for you, per the course’s policy on academic honesty.

The staff conducts random audits of submissions to CS50x. Students found to be in violation of this policy will be removed from the course. Students who have already completed CS50x, if found to be in violation, will have their CS50 Certificate permanently revoked.

What to Do

Log into cs50.dev using your GitHub account
Run update50 in your codespace’s terminal window to ensure your codespace is up-to-date and, when prompted, click Rebuild now
Submit Volume
Submit one of:
- this version of Filter if feeling less comfortable
- this version of Filter if feeling more comfortable
Submit Recover

When to Do It

The below deadline is the deadline to submit this version of this problem set, but the course’s overall deadline has already been extended to 30 June 2026.

Starting on 1 January 2026, you will have to use the 2026 version of this problem set, and won’t be able to submit this version any longer, which is why the deadline appears below as it does. But the course continues into 2026!

By 2025-12-31T23:59:00+00:00.

Advice

Try out any of David’s programs from Week 4.
If you see any errors when compiling your code with make, focus first on fixing the very first error you see, scrolling up as needed. If unsure what it means, try asking help50 for help. For instance, if trying to compile filter, and
```
make filter
```
is yielding errors, try running
```
help50 make filter
```
instead!