https://github.com/kaworu/adventofcode-2015

Advent of Code 2015 puzzles and solutions
https://github.com/kaworu/adventofcode-2015

awk coding-challenge

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Advent of Code 2015 puzzles and solutions

• Host: GitHub
• URL: https://github.com/kaworu/adventofcode-2015
• Owner: kaworu
• License: mit
• Created: 2016-12-03T06:48:04.000Z (about 9 years ago)
• Default Branch: master
• Last Pushed: 2021-09-12T21:46:47.000Z (over 4 years ago)
• Last Synced: 2025-01-22T05:17:11.471Z (about 1 year ago)
• Topics: awk, coding-challenge
• Language: Awk
• Homepage:
• Size: 150 KB
• Stars: 9
• Watchers: 5
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
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# Advent of Code 2015

https://adventofcode.com puzzles solutions in [AWK][].

> Advent of Code is a series of small programming puzzles for a variety of

> skill levels. They are self-contained and are just as appropriate for an

> expert who wants to stay sharp as they are for a beginner who is just

> learning to code. Each puzzle calls upon different skills and has two parts

> that build on a theme.

## Why AWK?

After solving the firsts two or three puzzle, I thought that AWK would be an

ideal language. The puzzle input is (usually) to be parsed either line-by-line

or sometimes character-by-character; AWK excel at both. As a results, solutions

contain very few parsing related lines of code and can be focused on the

problem.

## And?

Then _Day 04 - The Ideal Stocking Stuffer_ required to compute *a lot* of MD5

hashes and it became quite challenging due to AWK's limitations. Using pipe has

serious performance and portability impact, [dynamic extensions][] is limited

to Gawk and greatly limit usability. Implementing MD5 in pure AWK is tricky

because it lacks bitwise operators (Gawk and busybox awk have them though).

Also puzzles gets harder as days goes by, to the point that finding elegant AWK

solution become really challenging. The most outstanding limitations are:

- **There are very few built-in functions** and (almost) all of them are string

  processing functions. Hasn't been a big issue since most challenges are

  mathematical puzzles.

- **Only two scalar types** (if we omit regexp): strings and Double-precision

  floating-point numbers. This makes some stuff usually ubiquitous in "general

  purpose" programming languages (e.g. bitwise operations) a bit tricky.

- **It is not possible to return associative arrays from functions**. This can

  be worked around by passing an array as parameter that is to be modified by

  the function.

- **The only composite type — associative arrays — is not recursive** (values

  are limited to numbers or strings). Because of this, it is often hard to

  implement solutions able to solve the general case problem as they can

  require an "additional" dimension (e.g. 4 lines input vs arbitrary lines

  input). To work around this issue I've used multiple array subscripts (which

  is really only syntactic sugar), function recursion (basically using the call

  stack "as a dimension"), and serialization to string.

[AWK]: https://en.wikipedia.org/wiki/AWK

[dynamic extensions]: https://www.gnu.org/software/gawk/manual/html_node/Dynamic-Extensions.html