Programming, Topic: Graph Theory

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AoC 2024 Day 23: LAN Partinator

2024-12-23

Source: Day 23: LAN Party

Full solution for today (spoilers!).

Part 1

You are given the edges of an undirected graph. Count how many complete subgraphs of size three exist that contain one or more starting with the letter t.

Aside: Games with local (but not hotseat) multiplayer have gotten rather rarer over the years… how many people still know what a LAN party is/was?

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Infinite Craft Bot

2024-03-14

You’ve probably seen Neil.fun’s Infinite Craft game somewhere on the internet. If not, in a nutshell:

  • You start with 4 blocks: Earth, Fire, Water, and Wind.
  • You can combine any two blocks, for example:
    • Earth + Water = Plant
    • Plant + Fire = Smoke
    • Smoke + Smoke = Cloud

That’s… pretty much it, from a gameplay perspective. There’s not really any goal, other than what you set yourself (try to make Cthulhu!). Although if you manage to find something no one has ever made before, you get a neat little note for it!

So wait, what do I mean by ‘something no one has ever seen before’?

Well, if two elements have ever been combined by anyone before, you get a cached response. Barring resets of the game (no idea if / how often this has happened, but I assume it has), if A + B = C for you, A + B = C for everyone.

And here’s the fun part: if you find a combination no one has ever found before: Neil.fun will send the combination out to an LLM to generate the new answer. The specific prompt isn’t public (so far as I know), but essentially what that means is that you have a basically infinite crafting tree1!

So of course seeing something like this I want to automate it. 😄

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AoC 2022 Day 16: Pressurinator

2022-12-16

Source: Proboscidea Volcanium

Part 1

Given a graph of nodes, some of which have a pressure (per tick output value) and an agent that can move through the graph and activate specific nodes (so that they output their per tick value every future tick), what is the maximum total output possible in 30 steps?

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AoC 2017 Day 12: Gridlock

2017-12-12

Source: Digital Plumber

Part 1: A network of nodes is defined by a list of lines formatted as such:

2 <-> 0, 3, 4


> In this case, node `2` is connected to `0`, `3`, and `4` and vice versa.

> How many nodes are in the group that contains the node `0`?





First, load the data into an [[wiki:adjacency map]]():

```python
nodes = set()
neighbors = collections.defaultdict(set)

for line in lib.input():
    source, destinations = line.split('<->')
    source = int(source.strip())
    nodes.add(source)

    for destination in destinations.strip().split(','):
        destination = int(destination.strip())
        nodes.add(destination)

        neighbors[source].add(destination)
        neighbors[destination].add(source)

Then, write a function that can take a node and recursively expand until it finds all nodes in the same group:

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Cracker Barrel Peg Game, Part 2

2014-07-09

Hey, remember that post a few days ago about the Cracker Barrel peg game? Right at the end, I mentioned that there would be a part two, all about how to bend the puzzle at least a bit to your advantage. Basically, rather than finding the first solution to the peg game, we’re going to find all of them. From there, we can determine which moves are easier to win from, which are harder, and which are downright impossible. Let’s do it!

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Graph coloring

2014-01-15

Here’s another one from /r/dailyprogrammer:

… Your goal is to color a map of these regions with two requirements: 1) make sure that each adjacent department do not share a color, so you can clearly distinguish each department, and 2) minimize these numbers of colors.

Essentially, graph coloring.

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