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Just as a teaser for the next Advent of Code in 10 1/2 months, we would like to show a few pictures related to last edition. The 25 puzzles, data and solutions can be found here and here. They are programmed with HAC (the HAC Ada Compiler), thus in a small subset of the Ada language. The HAC compiler is very fast, so you run your program without noticing it was ever compiled, which is perfect for completing a programming puzzle.

Day 22 run with HAC (here, embedded in the LEA environment)

However, the program will run substantially slower than compiled with a native, optimizing compiler like GNAT.
This is not an issue for most Advent of Code puzzles, but for some, it is, especially on the later days. Fortunately, changing from HAC to GNAT is trivial (just switch compilers), unlike the traditional reprogramming of Python prototypes in C++, for instance.

The pictures

Day 8's data is a map representing the height of trees. Once the puzzle was solved, I was curious how the forest looked like. Note that different users get different data, so you are unlikely to find a visualisation of exactly your data on the internet.

Day 12's puzzle is a shortest path problem with specific rules and a nice data - a terrain with a hill - which seems designed to trap depth-first-search algorithms into an almost infinite search. The yellowish path is the shortest from the green dot, elevation 'a', to blue dot, elevation 'z'.
The pinkish path is the shortest from the blue dot to any dot with elevation 'a'. Fortunately Dijkstra's algorithm (and perhaps others) allows for such a special criterion regarding the end point.

Click to enlarge

For day 22’s puzzle, a walk on a cube’s surface is involved, so it is helpful to sketch it on a piece of paper, cut it and glue the faces. A banana skin of that puzzle is that the example’s layout may be different from the data’s layout. We slipped on that one and ended up gluing and programming the face-to-face transitions for two layouts…

Click to enlarge

Other Adaists’ solutions, discussions and pictures can be found here and in the "2022 Day x" threads in the same forum.

 Time for the family to celebrate... and to recover from the advent puzzles epidemic 😉

• Advent of Code - with solutions done with HAC
  
• Mathe im Advent
• MATH+ Adventskalender
• EXIT - Das Spiel: Adventskalender

Day 7 of the Advent of Code, titled "Handy Haversacks" is nice pair of puzzles involving recursion.

The data is a set of rules, beginning with

wavy green bags contain 1 posh black bag, 1 faded green bag, 4 wavy red bags.

dotted chartreuse bags contain 1 light beige bag.

dark white bags contain 2 dotted white bags.

... 

There are hundreds of such rules.

The puzzles involve recursion, which makes them fun.

You can see below HAC at work on the problem, from the LEA editor.

There is also a "full Ada" version. I began with that one, because the current limitations of HAC would have been too time-consuming (in terms of development time) for submitting a solution quickly enough. The limitations are not around recursion, that HAC masters like a big one, but mostly around the enumeration type I/O which is currently non-existent in HAC (v.0.081).

Click to enlarge

Solutions will be soon be posted on the HAC repositories.

First use of HAC, via the LEA editor, for the famous Advent of Code contest.

LEA screenshot: a parser for Day 2 Advent of Code's puzzle

In my (of course biased) opinion, LEA is perfect (among other tasks...) for developing quickly Ada solutions to the Advent of Code problems.

After the rush, I tidy up the source code with GNAT's style checks. Hence the presence of a GNAT project file, aoc_2020.gpr .

Then I post my solutions as HAC examples, here and here.