Intermediate Challenges

Description

Link to original Reddit submission

Thanks for that list you made me, my thoughts are way more organised!

I’ve got a few problems though that I thought you might be able to help with? Sometimes I put the wrong information in a list item. Maybe to prevent this I’d be able to modify/update the list item? That’s not the only problem though, when there are 50+ items it gets kind of hard to work my way through. Do you think you could maybe add the ability to categorise my items? Obviously, if I have that, I’d also like to be able to view by category!

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Description

Link to original Reddit submission

The challenge is to match a string like .--...-.-.-.....-.--........----.-.-..---.---.--.--.-.-....-..-...-.---..--.----.. to a permutation of the English alphabet that would produce it, e.g. wirnbfzehatqlojpgcvusyxkmd. Note that there may be more than one valid permutation.

Solution

I’m used to problems where the resources are not depleted, e.g. I can use a as many times as I want. The trickiest part was keeping track of the substring indexes.

Description

Link to original challenge

Most introductionary implementations for testing the primality of a number have a time complexity of $ O(\sqrt{n}) $. For large numbers this is not a feasible strategy, for example testing a 400 digit number . Fermat’s Little Theorem states:

If $p$ is a prime number, then for any integer $a$, the number $a^p − a$ is an integer multiple of $p$

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Description

Link to original problem

In computing, a linear-feedback shift register (LFSR) is a shift register whose input bit is a linear function of its previous state. The most commonly used linear function of single bits is exclusive-or (XOR). Thus, an LFSR is most often a shift register whose input bit is driven by the XOR of some bits of the overall shift register value.