Source: Trench Map

Part 1: Given a 9->1 cellular automota update function (take the pixel and 8 surrounding pixels as a 9-bit index into the function) and a binary image, apply the function twice and count the number of ’lit’ pixels. Assume that the canvas is infinite.

read more...

Source: Snailfish

Part 1: You will be given a series of Scanners, each of which will tell you the location (from their point of view) of a series of Beacons. Each Scanner may be flipped or rotated in increments of 90 degrees in any direction. Determine where each Scanner and Beacon is by overlaying the maps (with at least pairwise 12 matches).

read more...

Source: Snailfish

Part 1: Given the following definition of Snailfish numbers, add a series of Snailfish numbers and return the magnitude of the result.

read more...

Source: Packet Decoder

Part 1: Given a recursive binary packet definition (see below), parse the given packet. Return the sum of each packet’s version.

read more...

Source: Passage Pathing

Part 1: Given a list of edges in a bi-directional graph, count the number of paths from start to end such that nodes named with lowercase letters are visited once, and nodes with uppercase letters can be visited any number of times.

read more...

Source: Dumbo Octopus

Part 1: Simulate a grid of numbers such that on each tick: advance all numbers by 1, any number that increases over 9 will ‘flash’ and add 1 to all neighbors (recursively, but each cell can only flash once) and then reset to 0. Count the number of flashes in the first 100 ticks.

read more...

Source: Syntax Scoring

Part 1: Given a sequence of () [] {}, and <> with nesting allowed. Find the first syntax error (where the wrong closing symbol is used). Scoring 3, 57, 1197, and 25137 respectively for each error, calculate the total error score.

read more...

Source: Smoke Basin

Part 1: Given a heightmap, find all local minimums. Return the sum of (minimum height + 1) for each local minimum.

read more...

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:

read more...

Source: Recursive Circus

Part 1: A tree is defined as such:

• node (weight) -> child1, child2, ...
• node (weight)

Where a node always has a weight, but may or may not have child nodes.

What is the name of the root node of the tree (the node without a parent)?

read more...