advent_of_code_2021 VS aoc2021

I had the same approach. A bit different details in the end (double counting yadda yadda). Here is my code!

Link to code

This in C runs in 215 us on a Pi 4 with the cpu in performance mode: https://github.com/ednl/aoc2021/blob/main/day06.c

I took a few hints from the solutions thread and made this in C which executes in 0.4 milliseconds on a Raspberry Pi 4: https://github.com/ednl/aoc2021/blob/main/day06.c

Good outcome. I'm not well versed in C++ so I can't say much about it. For my solution in C, I figured that a full-blown tree was too much work and also not really needed if I kept track of the level myself, because everything is always in the same order left to right, just expanding and contracting. So I used a linked list and a SF number became an array of SF digits where each digit is a struct { left,right,level,value }. I guess the trickiest bit was to do the accountancy of keeping everything linked correctly when exploding and splitting.

The constant time thing is counting fish in an age histogram mod 9, right? I think that idea floated around the solution thread. I am no longer sure if I saw it there first or came up with it myself..... but here's my implementation in C: https://github.com/ednl/aoc2021/blob/main/day06.c

Added lots of comments as explanation of the ideas and the code: https://github.com/ednl/aoc2021/blob/main/day14.c

Good ol' C code. Very simple program once you think of making a circular buffer from the population histogram by age bins, and simulating every day. I got stuck for a while trying to come up with a direct mathematical function which never gave me the exact number. The crux:

C, which takes some bookkeeping but it can be fast. I didn't push for every last drop of speed but still: about 3 ms on a Raspberry Pi 4 (1.8 GHz overclock, Buster desktop, not very quiet so I picked a good run). Code with lots of comments