Posts tagged puzzle

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Advent of Code 2024 started today. This is my fifth year participating. Previous years were: 2020, 2021, 2022 and 2023.

Although I primarily use Racket for software development, I’ll be using Python this year to gain proficiency with the language in preparation for future data science and artificial intelligence work.

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#lang iracket/lang #:require racket
(require "../advent.rkt")

Day 8 involves navigating binary trees, and modular arithmetic, but I’m getting ahead of myself. Here is our test input:

RL

AAA = (BBB, CCC)
BBB = (DDD, EEE)
CCC = (ZZZ, GGG)
DDD = (DDD, DDD)
EEE = (EEE, EEE)
GGG = (GGG, GGG)
ZZZ = (ZZZ, ZZZ)

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#lang iracket/lang #:require racket
(require "../advent.rkt")

Day 7 involves simulating a card game. Our input looks like:

...
8J833 494
6AJT8 318
AA4QQ 125
62KK6 876
7A7QK 241
...

The left side is our card hand. The right side is our bid amount. As always, we begin with parsing. For our purposes of illustration, I’ll skip the first 20 hands to get to a more interesting one with a J:

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#lang iracket/lang #:require racket
(require "../advent.rkt")

Day 5 involves a typical Advent of Code scenario where Part 1 is easy, and a naive modification to Part 1 to get Part 2 is easy; however, the naive Part 2 solution will take far too long to run! :)

After solving Part 1 to get a star, I re-implemented the code to solve Part 2, and then Part 1 was simply making the Part 1 input conform to what Part 2 needed, and call Part 2.

The “trick” for Part 2 was to process the seed ranges as ranges, and not attempt to convert the seed ranges into lists of individual seeds.

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#lang iracket/lang #:require racket
(require "../advent.rkt")

I always enjoy recursive list processing in Racket :) Here’s our input today:

Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11

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#lang iracket/lang #:require racket
(require "../advent.rkt" threading)

Day 3 involves some two dimensional analysis, so we’ll use complex numbers as a convenient two dimensional index:

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#lang iracket/lang #:require racket
(require "../advent.rkt" threading)

Our data today is as follows:

Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green
Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green

For today’s task, I found it helpful to make use of the parallel-combine combinator from Hanson & Sussman’s “Software Design for Flexibility”. This combinator applies f and g to the input, in parallel, and combines their output using h. Pictorially, it looks like this: