This package contains the source and data for day 7 of the challenge.
- Status: Complete
- Difficulty Rating: 1.5 / 5
It could be really easy on this task to waste time trying to optimise a solution for part 1 only for it to be completely useless on part 2.
The key to these tasks is to follow the make it barely work principle for part 1, then once you have the full scope of part 2, start optimising from there.
The trick to part 2 was figuring out the fuel consumption for each movement is the triangular number of the flat consumption.
To be completely honest I couldn't remember what these numbers were called, so yes, I actually did google search additional-factorial to try and 'reverse-mathematics' my way to the wiki article.
I tried throwing an LRU cache at function that computes the triangular numbers, mostly just to see how much it'd help, I achieved around a 25% speedup at best. However, due to the wide range of input numbers, and the relatively low time-cost of the function anyway, I ended up just committing the solution without any caching.