This repo is a solution in Rust to the problem of "25 unique letters in 5 five-letter words" raised by Matt Parker (ie @standupmaths). The problem is explained in his video in detail.
Matt Parker's solution to this problem was "greatly inefficient" to say the least, which motivated me to attempt this problem.
Notably, I did not look at his follow-up video for ideas before the commit f332fca8.
To optimize the code, I basically done the following:
- Use a bit / bit mask representation for all the words and word sets.
- This reduces repetition check overhead by using bitwise and.
- This also removes all anagrams in the process.
- Build a map of all possible combinations of words that produced a set of unique letters.
To my surprise, some of these techniques were also used in the then optimal solution shown in his follow-up video.
My code resulted in a total runtime of about 300 seconds on a M1 Macbook Air, including writing the results and "bit representations" file.