this post was submitted on 26 Aug 2023
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Programming Challenges

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Welcome to the programming.dev challenge community!

Three challenges will be posted every week to complete

Easy challenges will give 1 point, medium will give 2, and hard will give 3. If you have the fastest time or use the least amount of characters you will get a bonus point (in ties everyone gets the bonus point)

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[Medium] String Decompression Solutions Counter (programming.dev)
submitted 1 year ago* (last edited 1 year ago) by Ategon@programming.dev to c/challenges@programming.dev
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Given a compressed string, give the number of ways it can be decompressed.

  • A compressed string is a string where substrings of repeated characters are changed to a format similar to aaa -> a3
  • For example for the string aaabbhhhh33aaa the compressed string would be a3b2h432a3

As an example of counting decompressing options. Say you have the input a333b2. This can be read as a333 b2 or a3 33 b2 so you would need to return the value 2 as there are 2 options.

You must accept the input as a command line argument (entered when your app is ran) and print out the result

(It will be called like node main.js aaaaa or however else to run apps in your language)

You can use the solution tester in this post to test you followed the correct format https://programming.dev/post/1805174

Checking through the solutions of last weeks problems should be happening ~~this weekend~~ monday + tuesday. Been getting too much work and theres a game jam thats been going on but should be able to go through them all then. I may do the easy one last since it cant be checked using the solutions tester so that one will take a bit longer.

Will also try to go through and give solutions to these ones as well on the weekend and will try to do solutions as soon as possible from now on so you can see if you failed the test cases. For the ones done last week, after I go through them all ill give 1 extra day from then on for any resubmissions

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[–] Quasari@programming.dev 3 points 1 year ago (1 children)

Without memoization, I believe the Fibonacci sequence is O(2^N). It's dependent on how long a sequence of digits is in the input, so your worst case is like O(2^N) if the string is mostly digits and best case being O(N) if there are only 1 or 2 digit sequences.

Someone can correct me if I'm wrong.

[–] shape-warrior-t@kbin.social 1 points 1 year ago (1 children)

My implementation is memoized by functools.cache, but that is a concern when it comes to recursive Fibonacci. That, and stack overflows, which are also a problem for my code (but, again, not for "reasonable" inputs -- fibonacci(94) already exceeds 2^64).

Time complexity-wise, I was more thinking about the case where the numbers get so big that addition, multiplication, etc. can no longer be modelled as taking constant time. Especially if math.prod and enumerate are implemented in ways that are less efficient for huge integers (I haven't thoroughly checked, and I'm not planning to).

[–] Quasari@programming.dev 2 points 1 year ago

functools.cache

That's pretty cool. I haven't dived too deep into python, so I should of looked up the library when you attached the @cache decorator. I learned something.