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.

What to Do

Log into code.cs50.io 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 one of:
- Filter (Less) if feeling less comfortable
  Getting Started
  
  Start by clicking inside your terminal window, then execute cd by itself. You should find that its “prompt” resembles the below.
```
$
```
  Click inside of that terminal window and then execute
```
wget https://cdn.cs50.net/2022/fall/psets/4/filter-less.zip
```
  followed by Enter in order to download a ZIP called filter-less.zip in your codespace. Take care not to overlook the space between wget and the following URL, or any other character for that matter!
  
  Now execute
```
unzip filter-less.zip
```
  to create a folder called filter-less. You no longer need the ZIP file, so you can execute
```
rm filter-less.zip
```
  and respond with “y” followed by Enter at the prompt to remove the ZIP file you downloaded. Finally, right-click or control-click on the filter-less folder and click “Open in CS50 Lab”. You should see the specification for this problem on the left-hand side and its distribution code on the right-hand side.
- Filter (More) if feeling more comfortable
  Getting Started
  
  Start by clicking inside your terminal window, then execute cd by itself. You should find that its “prompt” resembles the below.
```
$
```
  Click inside of that terminal window and then execute
```
wget https://cdn.cs50.net/2022/fall/psets/4/filter-more.zip
```
  followed by Enter in order to download a ZIP called filter-more.zip in your codespace. Take care not to overlook the space between wget and the following URL, or any other character for that matter!
  
  Now execute
```
unzip filter-more.zip
```
  to create a folder called filter-more. You no longer need the ZIP file, so you can execute
```
rm filter-more.zip
```
  and respond with “y” followed by Enter at the prompt to remove the ZIP file you downloaded. Finally, right-click or control-click on the filter-more folder and click “Open in CS50 Lab”. You should see the specification for this problem on the left-hand side and its distribution code on the right-hand side.
Submit one of:
- Recover
  Getting Started
  
  Start by clicking inside your terminal window, then execute cd by itself. You should find that its “prompt” resembles the below.
```
$
```
  Click inside of that terminal window and then execute
```
wget https://cdn.cs50.net/2022/fall/psets/4/recover.zip
```
  followed by Enter in order to download a ZIP called recover.zip in your codespace. Take care not to overlook the space between wget and the following URL, or any other character for that matter!
  
  Now execute
```
unzip recover.zip
```
  to create a folder called recover. You no longer need the ZIP file, so you can execute
```
rm recover.zip
```
  and respond with “y” followed by Enter at the prompt to remove the ZIP file you downloaded. Finally, right-click or control-click on the recover folder and click “Open in CS50 Lab”. You should see the specification for this problem on the left-hand side and its distribution code on the right-hand side.
- Reverse
  Getting Started
  
  Start by clicking inside your terminal window, then execute cd by itself. You should find that its “prompt” resembles the below.
```
$
```
  Click inside of that terminal window and then execute
```
wget https://cdn.cs50.net/2022/fall/psets/4/reverse.zip
```
  followed by Enter in order to download a ZIP called reverse.zip in your codespace. Take care not to overlook the space between wget and the following URL, or any other character for that matter!
  
  Now execute
```
unzip reverse.zip
```
  to create a folder called reverse. You no longer need the ZIP file, so you can execute
```
rm reverse.zip
```
  and respond with “y” followed by Enter at the prompt to remove the ZIP file you downloaded. Finally, right-click or control-click on the reverse folder and click “Open in CS50 Lab”. You should see the specification for this problem on the left-hand side and its distribution code on the right-hand side.
Submit this form

If you submit both versions of Filter, we’ll record the higher of your two scores. If you submit both Recover and Reverse, we’ll similarly record the higher of your two scores.

When to Do It

By 2022-10-02T23:59:00-04:00.

How to Get Help

Browse or search for answers on Ed or post your own questions!
Browse the CS50 Manual Pages for functions that might be useful.
Watch Shorts for any topics that you still have questions about.
Sign up for a tutorial!
Attend office hours!

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!