59 lines
1.7 KiB
Text
59 lines
1.7 KiB
Text
|
Day 24 Notes
|
||
|
|
||
|
+--------+
|
||
|
| Part 1 |
|
||
|
+--------+
|
||
|
|
||
|
$ elixir day24part1.exs
|
||
|
326
|
||
|
|
||
|
Thoughts:
|
||
|
|
||
|
Interesting. Need to work out how to implement a hexagonal grid.
|
||
|
|
||
|
Use Enum.chunk_while to parse the variable-length `e`, `ne`, `s', `sw` etc. input tokens.
|
||
|
|
||
|
I decided to do it like this: Use x, y coordinates, but horizontally adjacent cells are 2 x units
|
||
|
apart. Diagonally adjacent cells are 1 x unit and 1 y unit apart.
|
||
|
|
||
|
/ \ (0,0)
|
||
|
| |
|
||
|
/ \ / \ (1, -1)
|
||
|
| | |
|
||
|
\ / \ /
|
||
|
↑
|
||
|
(-1, -1)
|
||
|
|
||
|
Define a tranlation vector for each direction, then we can walk the directions, and take the sum
|
||
|
of all the translations.
|
||
|
|
||
|
Store the black cells in a MapSet, and count them once we're done.
|
||
|
|
||
|
+--------+
|
||
|
| Part 2 |
|
||
|
+--------+
|
||
|
|
||
|
$ elixir day24part2.exs
|
||
|
3979
|
||
|
|
||
|
Thoughts:
|
||
|
|
||
|
More complicated now, because we actually have to iterate all the black/white cells and their
|
||
|
neighbours. Calculating the grid extremities looks complicated due to the hexagonal properties.
|
||
|
However, this is very similar to Day 17 Part 2, so I will just adapt that solution for here too:
|
||
|
|
||
|
1. For all current black squares, check the neighbours to see what its next state should be.
|
||
|
- additionally keep track of which white squares we identified.
|
||
|
2. As white cells must have a black neighbour to be flipped, we know that it's fine to only
|
||
|
check white cells that are next to a black cell. So iterate the white cells we encountered
|
||
|
in step 1, and check their neighbours too.
|
||
|
|
||
|
|
||
|
+------------------+
|
||
|
| Overall Thoughts |
|
||
|
+------------------+
|
||
|
|
||
|
Let another game of life. 3rd time this year? This one was a bit more interesting due to the
|
||
|
hexagonal nature, but part two was almost the same as Day 17. Maybe that's a good reflection
|
||
|
on my day 17 implementation, though.
|