## Advent of Code, in Erlang: Day 25

Wednesday, December 29, 2021

And so we reach the end of the Advent of Code. The final puzzle, Day 25, is straightforward, if a little tricky to get the what-was-what-is states correct. My code is in my github repo, but as it's just another list-walking substitution, I don't think it's worth discussing here. Instead, in this post I'll share my thoughts on the event.

## Advent of Code, in Erlang: Day 24

Tuesday, December 28, 2021

I almost wonder if I would have had a quicker solution time on Advent of Code's Day 24 puzzle if I had tried to do it while distracted with holiday celebrations, instead of deciding there was no way I could attempt it without clear focus time. I spun my wheels for a long time overengineering part of the solution, because I had convinced myself after a first, quick, read that this problem was reversing a hash, and so its search space would be huge, even after I figured out the "trick". It's not pencil-and-paper small with my final technique, but it is still milliseconds-of-computer-time small all the same.

## Advent of Code, in Erlang: Day 23

Saturday, December 25, 2021

Between a complicated Day 23 puzzle, and last-minute holiday gift work (and holiday celebration!), I've fallen behind in Advent of Code. But, I do finally have a solution for Day 23, so let's dig in.

## Advent of Code, in Erlang: Day 11

Thursday, December 23, 2021

I haven't tried Advent of Code Day 23 yet. I want to think about which approach to take. While I'm delaying that, why don't we talk about a puzzle writeup I've been delaying - Day 11.

## Advent of Code, in Erlang: Day 22

Wednesday, December 22, 2021

Twenty-two days into Advent of Code, it finally happened: I predicted what Part 2 would require! Not that I let the prediction guide me away from an overly simple Part 1 implementation, that I knew I would throw away. But I saw it coming.

## Advent of Code, in Erlang: Day 21

Tuesday, December 21, 2021

I don't often rewrite everything between Part 1 and Part 2 of the Advent of Code puzzles. But I sure did for Day 21.

## Advent of Code, in Erlang: Day 10

Monday, December 20, 2021

Ah, parenthesis/brace/bracket balancing. A classic. Using the right-hand-rule on Day 19, was not the first time the Advent of Code has given me college flashbacks. Day 10 could have come off a 6.001 problem set.

## Advent of Code, in Erlang: Day 20

Monday, December 20, 2021

I considered doing more bit mashing, bit masking, bit matching today. I really did. Advent of Code, Day 20 backs the time commitment down from Day 19 far enough that it was tempting to spend time on efficiency. But a very tiny amount of pre-processing of these images and enhancement algorithms, makes a simpler route much more fun:

## Advent of Code, in Erlang: Day 9

Monday, December 20, 2021

While we give people a few more hours to recover from Day 19 and delight in the relative ease of Day 20, let's take a trip back through time and discuss Advent of Code, Day 9. We're back to looking at a tile of numbers, and comparing them to their neighbors.

## Advent of Code, in Erlang: Day 19

Sunday, December 19, 2021

Oh, the irony of writing about the day that people complained about most, on the day that people were about to complain about even more! Since the Day 19 puzzle has been released, I've seen cries everywhere from, "I'm tapping out," to, "End me." I also was not sure I was going to be able to solve it at first, but I dove in anyway, starting with my secret weapon: sleep.

## Advent of Code, in Erlang: Day 8

Saturday, December 18, 2021

Looking at memes in the various Advent of Code 2021 threads, there is one day that seems to have more complaints than any other: Day 8, the scrambled seven-segment LED.

## Advent of Code, in Erlang: Day 18

Saturday, December 18, 2021

If you're looking at the per-day leaderboard (an activity I don't recommend spending too much time on, but is fun anyway), it's easy to see the puzzles are heating up! The longest first time to both stars before this was Day 16 at 9:52. Today, it nearly doubled to 17:13! What's going on?

## Advent of Code, in Erlang: Day 7

Friday, December 17, 2021

Oh good, this series has made it to Day 7, the day that I wasn't sure my code was "right", but did give the correct answer.

## Advent of Code, in Erlang: Day 17

Friday, December 17, 2021

Calling it "Advent of Code" sort of presupposes that there should be code involved. Without starting a flamewar about what is and isn't code, I want to say: sometimes you really don't need code to answer the puzzle.

## Advent of Code, in Erlang: Day 16

Thursday, December 16, 2021

The storm I was worried about mainly went south of me. The local airport weather records say our winds topped out at a brief 35mph sustained, and one 40mph gust. Starlink kept right on shuttling bits the whole time, so I was able to check out Advent of Code 2021, Day 16 right away.

## Advent of Code, in Erlang: Day 6

Thursday, December 16, 2021

It's fun revisiting the earlier puzzles to write about them after having done the later puzzles. Similarities show up that I hadn't considered at the time. For example, Day 6, which has the same sort of modeling-space growth problem as Day 14.

## Advent of Code, in Erlang: Day 5

Thursday, December 16, 2021

There's probably a good way to solve Advent of Code 2021, Day 5 without actually rendering the lines, as shown in the puzzle description, but rendering the lines provided such a good debugging aid that I couldn't see bothering with other methods.

## Advent of Code, in Erlang: Day 15

Wednesday, December 15, 2021

Remember on Day 12, when I said I wasn't particularly well versed in path plotting? Welcome to Advent of Code 2021, Day 15, where that's the name of the game. We have to find the "path of least risk" through a grid of tiles with varying risk levels. This one took me a while.

## Advent of Code, in Erlang: Day 4

Wednesday, December 15, 2021

Here I've been going on and on about how recent Advent Of Code days have had more complex parsing than earlier days, when I completely forgot about Bingo on Day 4. The timestamp in the git repo says I finished this puzzle at 6pm. I think the fact that I was hungry for dinner shows in the code.

## Advent of Code, in Erlang: Day 14

Tuesday, December 14, 2021

Okay, Day 14 of Advent of Code 2021 was fun. I had a good time solving it last night, and had a good time again cleaning up that code to share this morning.

## Advent of Code, in Erlang: Day 3

Tuesday, December 14, 2021

Wasn't I just talking about enjoying Erlang's binary/bit-level pattern matching? Today is full of it!

## Advent of Code, in Erlang: Day 13

Monday, December 13, 2021

After posting Day 1's write-up, I had about half an hour before the Day 13 puzzle was released. I stepped away from my computer, and played guitar … for an hour. After that, I could feel the day's cross-country skiing catching up, so I decided to stretch. And after that I decided it was too late, and I should just sleep and tackle Day 13 in the morning.

## Advent of Code, in Erlang: Day 2

Monday, December 13, 2021

While I wait for it to get a little later into Day 13, before posting spoilers for those that haven't solved it yet, let's talk about Day 2.

## Advent of Code, in Erlang: Day 1

Sunday, December 12, 2021

While I'm waiting for the Day 13 puzzle to unlock, let's jump back in time and talk about Advent of Code Day 1. This one was a nice smoke test to demonstrate how the puzzle workflow goes. Get an evironment set up. Read and parse a file. Learn that the second half will use the same input, but alter the analysis in some way.