I was reviewing the released practice exam and there is a problem that refers to 4.2.2 Explain the difference between solvable and unsolvable problems in CS and 4.2.1 Explain the difference between algorithms that run in a reasonable time and those that do not and 4.2.3 Explain the existence of undecidable problems in CS.

I see these objectives are listed in Unit 4 Lesson 7 (Public key cryptography).

Would one-way functions (mod math) going in reverse be considered a problem that does not run in a reasonable amount of time or unsolvable? Is there an example in the Code.org curriculum of an undecidable problem in CS? CB says that the problem of determining if any program will eventually stop cannot be solved by an algorithm so is an unsolvable problem.

We touch upon this in Unit 2 (heuristics). Finding the absolute most efficient compression in the lossless text compression widget I think is explained as being a problem that would take an unreasonable amount of timeâ€¦is this a correct interpretation?

Thanks in advance!

Alice