# Tag Info

### CS50AP vs CS50X which one or more thorough?

CS50 AP covers all the same material as CS50x but with additional problem sets (both programming based and writing based) and some extra curriculum that is required for the AP. It is a 36 week course,...
• 18.3k
1 vote
Accepted

### Is the Credit Problem required?

It's an extra problem for your own learning. It's not required for the certificate and can be submitted but is entirely optional. You can see the list of problems that are strictly optional (marked ...
• 18.3k
1 vote

### Sudoku, prevent user from deleting numbers on the original board

So this is about Sudoku, part of Chapter 4, Module 2 of CS50 AP (not CS50x). You made a mistake with for (int j = 0; j < 9; j++), you used i instead of j, so you accidentally copy only the first ...
• 20.7k
1 vote
Accepted

### CS50 AP Game of Fifteen

The won() function won't return a true win. Look at the following code: for (int i = 0, z = d; i < z; i++) { for (int ii = 0, zz = d; ii < zz; ii++) { if (checker[i][ii] == ...
• 63.4k
1 vote
Accepted

### Find's sort: instructions vs code: O(n) or O

Follow the spec. The problem uses the same distro code for both the "less" and "more" versions, so the TODO is based on the "less" specs.
• 18.3k
1 vote
Accepted

### Minor typo in cs50ap find docs?

That's not a typo. You might notice the footnote link at the end of that sentence that leads to this: This isn’t necessarily the best practice; you’d typically have all your prototypes in ...
• 18.3k
1 vote
Accepted

### How long are the passwords for crack?

Looks like a copy/paste error. We've updated the spec with the correct information. The passwords can indeed be up to 5 chars long. We also updated the 10 sample hashes.
• 18.3k
1 vote
Accepted

### Basic use of crypt in crack.c? (Hash "ROLF")

Unfortunately, there was a typo in the spec. The first example given was correct: ./crack 50fkUxYHbnXGw rofl but when repeated later in the spec, it showed ROFL in error. This has been ...
• 18.3k
1 vote
Accepted

### crack.c: error: implicit declaration of function 'crypt' is invalid in C99

The spec is perfectly correct. More than likely, you don't have #define _XOPEN_SOURCE #include <unistd.h> At the very top of your program (ie, before any other #includes). If you move that ...
• 18.3k

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