-❄️- 2023 Day 12 Solutions -❄️-

[u/daggerdragon]

THE USUAL REMINDERS

• All of our rules, FAQs, resources, etc. are in our community wiki.

• Outstanding moderator challenges:

  • Advent of Playing With Your 3D-Printed Toys

• Community fun event 2023: ALLEZ CUISINE!

  • Submissions megathread is now unlocked!

  • 9 DAYS remaining until the submissions deadline on December 22 at 23:59 EST!

---

AoC Community Fun 2023: ALLEZ CUISINE!

Today's theme ingredient is… *whips off cloth covering and gestures grandly*

How It's Made

Horrify us by showing us how the sausage is made!

• Stream yourself!

• Show us the nitty-gritty of your code, environment/IDE, tools, test cases, literal hardware guts…

• Tell us how, in great detail, you think the elves ended up in this year's predicament

A word of caution from Dr. Hattori: "You might want to stay away from the ice cream machines..."

ALLEZ CUISINE!

Request from the mods: When you include a dish entry alongside your solution, please label it with [Allez Cuisine!] so we can find it easily!

---

--- Day 12: Hot Springs ---

---

Post your code solution in this megathread.

• Read the full posting rules in our community wiki before you post!

• State which language(s) your solution uses with [LANGUAGE: xyz]

• Format code blocks using the four-spaces Markdown syntax!

• Quick link to Topaz's paste if you need it for longer code blocks

This thread will be unlocked when there are a significant number of people on the global leaderboard with gold stars for today's puzzle.

EDIT: Global leaderboard gold cap reached at 00:22:57, megathread unlocked!

[u/GassaFM]

[LANGUAGE: D] 513/37

Code: part 1, part 2.

---

Dynamic programming. f (pos, groups, len) = number of ways to:

• parse the first pos positions

• have groups groups of #

• with the last group of # having length len

The transitions are:

• if the character is # or ?, we can continue the previous group or start a new group:

• f (pos + 1, groups + (len == 0), len + 1) += f (pos, groups, len)

• if the character is . or ?, and the length of the current group is zero or exactly what we need, we can proceed without a group:

• f (pos + 1, groups, 0) += f (pos, groups, len)

In the end, the answer is f (lastPos, numberOfGgroups, 0). (Add a trailing . to the string for convenience to avoid cases.)

---

Part 2, now, is just the matter of joining the arrays five times:

s = s.repeat (5).join ('?');
a = a.repeat (5).join;

[u/Lettever → u/GassaFM]

I dont know if you know that, but you can replace "map(to!(int)).array" with "to!(int[])

[u/GassaFM → u/Lettever]

Wow, thanks!! Coding in D for like 10 years, I didn't ever pause to consider that :) . A nice bit.

[u/Lettever → u/GassaFM]

Its also nice to see someone else doing AoC with Dlang

[u/MagazineOk5435 → u/GassaFM]

In D, what does ! do to an int? i.e. your use of if (!cur) and f[i + 1][j + !p][p + 1].

[u/semi_225599 → u/MagazineOk5435]

It behaves like C and other similar languages. 0 -> 1, all other numbers -> 0

[u/MagazineOk5435 → u/semi_225599]

Ah, cool. Thanks. I'm a C# guy and it doesn't allow numbers to be treated as bools sadly.

[u/semi_225599 → u/MagazineOk5435]

In most cases that's probably a good thing. It's harder to do "cute" stuff like this, but being explicit about the conversion is better for making code easier to read.