45 lines
1.5 KiB
Text
45 lines
1.5 KiB
Text
|
Day 17 Notes
|
||
|
|
|
||
|
|
+--------+
|
||
|
|
| Part 1 |
|
||
|
|
+--------+
|
||
|
|
|
||
|
|
$ elixir day17part1.exs
|
||
|
|
362
|
||
|
|
|
||
|
|
Thoughts:
|
||
|
|
|
||
|
|
The answer is not pretty, but it works.
|
||
|
|
|
||
|
|
Rather than iterate through the entire coordinate plane, which would require keeping track of where
|
||
|
|
the current extremities are, I decided to only keep the set of active cubes around. Then for each
|
||
|
|
iteration, check all the active cube's neighbours.
|
||
|
|
|
||
|
|
In addition to counting the neighbours for the active cube, keep track of the inactive neighbours,
|
||
|
|
then check *their* neighbours too to see if they should become active.
|
||
|
|
|
||
|
|
+--------+
|
||
|
|
| Part 2 |
|
||
|
|
+--------+
|
||
|
|
|
||
|
|
$ elixir day17part2.exs
|
||
|
|
1980
|
||
|
|
|
||
|
|
Thoughts:
|
||
|
|
|
||
|
|
In Part 1 I was half expecting a high iteration count for part 2, hence why I avoided iterating the
|
||
|
|
entire plane. Instead, adding a 4th dimension was a two-line change :-)
|
||
|
|
|
||
|
|
+------------------+
|
||
|
|
| Overall Thoughts |
|
||
|
|
+------------------+
|
||
|
|
|
||
|
|
Nice to have a quick Part 2 solve after day 18 which took me ages. I probably dug myself into
|
||
|
|
a hole on day 18 though and should have took a step back and tried with a clearer mind.
|
||
|
|
|
||
|
|
I spent quite a while getting distracted by the examples, because they present a sliding plane.
|
||
|
|
Turns out I had actually written the correct implementation, I just struggled to translate my
|
||
|
|
coordinates to the graphical examples. Running the script produced the correct answer though, but
|
||
|
|
I cross-referenced it with one of the confusing examples, just in case it wasn't pure luck. I'm
|
||
|
|
glad I was able to solve Part 2 without reading all the dreaded 4D examples there too!
|