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Documentation Index

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Advent of Code 2020 is a complete year — all 25 days solved, both parts, with tests passing for every puzzle. The year’s theme follows a tropical vacation disrupted by global chaos, featuring puzzles centred on passport validation, bag rules, cellular automata, and even a sea-monster hunt inside a jigsaw of image tiles. Day 1 earned a top-100 score on the global leaderboard (38 points for Part 1).

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Progress

DayTitlePart 1Part 2Tests
01Report Repair⭐⭐✅
02Password Philosophy⭐⭐✅
03Toboggan Trajectory⭐⭐✅
04Passport Processing⭐⭐✅
05Binary Boarding⭐⭐✅
06Custom Customs⭐⭐✅
07Handy Haversacks⭐⭐✅
08Handheld Halting⭐⭐✅
09Encoding Error⭐⭐✅
10Adapter Array⭐⭐✅
11Seating System⭐⭐✅
12Rain Risk⭐⭐✅
13Shuttle Search⭐⭐✅
14Docking Data⭐⭐✅
15Rambunctious Recitation⭐⭐✅
16Ticket Translation⭐⭐✅
17Conway Cubes⭐⭐✅
18Operation Order⭐⭐✅
19Monster Messages⭐⭐✅
20Jurassic Jigsaw⭐⭐✅
21Allergen Assessment⭐⭐✅
22Crab Combat⭐⭐✅
23Crab Cups⭐⭐✅
24Lobby Layout⭐⭐✅
25Combo Breaker⭐⭐✅

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Notable Solutions

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Day 4 — Passport Processing

Part 1 checks that all required fields (byr, iyr, eyr, hgt, hcl, ecl, pid) are present. Part 2 adds strict validation: birth year must be a 4-digit number in [1920, 2002], height must be in the correct range for cm or in units, hair colour must match #rrggbb, and so on. Each rule is handled by an explicit if branch, making the validation logic easy to audit.

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Day 17 — Conway Cubes

The solution is dimension-agnostic. Active cells are stored in a set[Point] where Point is a tuple of arbitrary length. A cached neighbors function generates all 3^n - 1 neighbours for an n-dimensional point using itertools.product. Part 1 runs 3-D Game-of-Life for 6 cycles; Part 2 simply passes dimensions=4 to the same solve function. 
@functools.cache
def neighbors(p: Point) -> tuple[Point, ...]:
    return tuple(
        tuple(x + d for x, d in zip(p, deltas, strict=True))
        for deltas in itertools.product(*itertools.repeat((-1, 0, 1), len(p)))
        if any(x != 0 for x in deltas)
    )

part_1 = solve
part_2 = functools.partial(solve, dimensions=4)

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Day 20 — Jurassic Jigsaw

Each Tile wraps a NumPy array so that rotations and reflections are handled with np.rot90 and np.flip. Tiles are matched edge-to-edge by comparing border strings. Once all tiles are assembled into a grid, the combined image is scanned for the sea-monster pattern using a set of known relative offsets, and the total # count minus found sea-monster # cells gives the answer.
Puzzle inputs are personal and are not stored in this repository. Solutions fetch input at runtime using aocd (aocd.data).

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