Advent of Code notes

Year	Language
2019
2020
2021
2022
2023
2024
2025

See blog for the story.

Arcade game (4)BFS/DFS (21)Binary search (1)Bitwise operations (4)Brute force (17)Cellular automata (8)Constraint satisfaction (4)Coordinate compression (3)Data structures (23)Dijkstra (5)Dynamic programming (10)Geometry (21)Graph theory (4)Greedy (1)Grid walking (14)Image processing (4)Intcode (12)Manual inspection (14)Mathematics (15)Maze (6)Memoization (7)Modular arithmetic (4)Parsing (3)Period finding (5)Physics (3)Puzzle (18)Recursion (3)String manipulation (5)VM (4)

Year	Day	Title	Links	Tags
2025	1	Secret Entrance	Prob \| Src \| Notes	Brute forceMathematics
2025	2	Gift Shop	Prob \| Src \| Notes	Brute forceMathematics
2025	3	Lobby	Prob \| Src \| Notes	Greedy
2025	4	Printing Department	Prob \| Src \| Notes	Cellular automata
2025	5	Cafeteria	Prob \| Src \| Notes	Geometry
2025	6	Trash Compactor	Prob \| Src \| Notes	String manipulation
2025	7	Laboratories	Prob \| Src \| Notes	Dynamic programming
2025	8	Playground	Prob \| Src \| Notes	Data structures
2025	9	Movie Theater	Prob \| Src \| Notes	GeometryCoordinate compression
2025	10	Factory	Prob \| Src \| Notes	BFS/DFSMathematics
2025	11	Reactor	Prob \| Src \| Notes	Graph theory
2025	12	Christmas Tree Farm	Prob \| Src \| Notes	Puzzle
2024	1	Historian Hysteria	Prob \| Src \| Notes	Data structures
2024	2	Red-Nosed Reports	Prob \| Src \| Notes	Mathematics
2024	3	Mull It Over	Prob \| Src \| Notes	String manipulation
2024	4	Ceres Search	Prob \| Src \| Notes	Grid walking
2024	5	Print Queue	Prob \| Src \| Notes	Brute force
2024	6	Guard Gallivant	Prob \| Src \| Notes	Grid walkingBrute force
2024	7	Bridge Repair	Prob \| Src \| Notes	BFS/DFS
2024	8	Resonant Collinearity	Prob \| Src \| Notes	Geometry
2024	9	Disk Fragmenter	Prob \| Src \| Notes	Data structures
2024	10	Hoof It	Prob \| Src \| Notes	Dynamic programming
2024	11	Plutonian Pebbles	Prob \| Src \| Notes	Dynamic programming
2024	12	Garden Groups	Prob \| Src \| Notes	Geometry
2024	13	Claw Contraption	Prob \| Src \| Notes	Mathematics
2024	14	Restroom Redoubt	Prob \| Src \| Notes	Grid walkingManual inspection
2024	15	Warehouse Woes	Prob \| Src \| Notes	Arcade gameBFS/DFS
2024	16	Reindeer Maze	Prob \| Src \| Notes	MazeDijkstra
2024	17	Chronospatial Computer	Prob \| Src \| Notes	VMManual inspectionBitwise operationsPuzzle
2024	18	RAM Run	Prob \| Src \| Notes	BFS/DFSData structuresGeometry
2024	19	Linen Layout	Prob \| Src \| Notes	Memoization
2024	20	Race Condition	Prob \| Src \| Notes	Geometry
2024	21	Keypad Conundrum	Prob \| Src \| Notes	PuzzleMemoization
2024	22	Monkey Market	Prob \| Src \| Notes	Bitwise operationsData structures
2024	23	LAN Party	Prob \| Src \| Notes	Graph theory
2024	24	Crossed Wires	Prob \| Src \| Notes	PuzzleConstraint satisfactionManual inspection
2024	25	Code Chronicle	Prob \| Src \| Notes
2023	1	Trebuchet?!	Prob \| Src \| Notes	String manipulation
2023	2	Cube Conundrum	Prob \| Src \| Notes	Data structures
2023	3	Gear Ratios	Prob \| Src \| Notes	Image processing
2023	4	Scratchcards	Prob \| Src \| Notes
2023	5	If You Give A Seed A Fertilizer	Prob \| Src \| Notes	MathematicsPuzzle
2023	6	Wait For It	Prob \| Src \| Notes	Mathematics
2023	7	Camel Cards	Prob \| Src \| Notes	Data structuresPuzzle
2023	8	Haunted Wasteland	Prob \| Src \| Notes	Period finding
2023	9	Mirage Maintenance	Prob \| Src \| Notes	Mathematics
2023	10	Pipe Maze	Prob \| Src \| Notes	Grid walkingGeometry
2023	11	Cosmic Expansion	Prob \| Src \| Notes	Puzzle
2023	12	Hot Springs	Prob \| Src \| Notes	Dynamic programming
2023	13	Point of Incidence	Prob \| Src \| Notes	Geometry
2023	14	Parabolic Reflector Dish	Prob \| Src \| Notes	Arcade gamePeriod finding
2023	15	Lens Library	Prob \| Src \| Notes	Data structures
2023	16	The Floor Will Be Lava	Prob \| Src \| Notes	Grid walkingBFS/DFS
2023	17	Clumsy Crucible	Prob \| Src \| Notes	Grid walkingDijkstra
2023	18	Lavaduct Lagoon	Prob \| Src \| Notes	Coordinate compressionGeometry
2023	19	Aplenty	Prob \| Src \| Notes	BFS/DFSGeometry
2023	20	Pulse Propagation	Prob \| Src \| Notes	BFS/DFSPuzzleManual inspectionPeriod finding
2023	21	Step Counter	Prob \| Src \| Notes	BFS/DFSPuzzleManual inspectionGeometry
2023	22	Sand Slabs	Prob \| Src \| Notes	BFS/DFS
2023	23	A Long Walk	Prob \| Src \| Notes	MazeGraph theoryBFS/DFSManual inspection
2023	24	Never Tell Me The Odds	Prob \| Src \| Notes	GeometryMathematics
2023	25	Snowverload	Prob \| Src \| Notes	Graph theoryManual inspection
2022	1	Calorie Counting	Prob \| Src \| Notes	Brute force
2022	2	Rock Paper Scissors	Prob \| Src \| Notes	Brute force
2022	3	Rucksack Reorganization	Prob \| Src \| Notes	Data structures
2022	4	Camp Cleanup	Prob \| Src \| Notes	Data structures
2022	5	Supply Stacks	Prob \| Src \| Notes	Data structures
2022	6	Tuning Trouble	Prob \| Src \| Notes	Data structures
2022	7	No Space Left On Device	Prob \| Src \| Notes	Data structuresPuzzle
2022	8	Treetop Tree House	Prob \| Src \| Notes	Memoization
2022	9	Rope Bridge	Prob \| Src \| Notes	Grid walking
2022	10	Cathode-Ray Tube	Prob \| Src \| Notes	VMManual inspection
2022	11	Monkey in the Middle	Prob \| Src \| Notes	Modular arithmetic
2022	12	Hill Climbing Algorithm	Prob \| Src \| Notes	BFS/DFSMaze
2022	13	Distress Signal	Prob \| Src \| Notes	ParsingRecursion
2022	14	Regolith Reservoir	Prob \| Src \| Notes	Physics
2022	15	Beacon Exclusion Zone	Prob \| Src \| Notes	GeometryPuzzle
2022	16	Proboscidea Volcanium	Prob \| Src \| Notes	BFS/DFSDynamic programming
2022	17	Pyroclastic Flow	Prob \| Src \| Notes	Arcade gamePeriod finding
2022	18	Boiling Boulders	Prob \| Src \| Notes	BFS/DFS
2022	19	Not Enough Minerals	Prob \| Src \| Notes	Dynamic programming
2022	20	Grove Positioning System	Prob \| Src \| Notes	Data structures
2022	21	Monkey Math	Prob \| Src \| Notes	Mathematics
2022	22	Monkey Map	Prob \| Src \| Notes	Grid walkingGeometry
2022	23	Unstable Diffusion	Prob \| Src \| Notes	Cellular automata
2022	24	Blizzard Basin	Prob \| Src \| Notes	BFS/DFS
2022	25	Full of Hot Air	Prob \| Src \| Notes	Mathematics
2021	1	Sonar Sweep	Prob \| Src \| Notes	Brute forceMathematics
2021	2	Dive!	Prob \| Src \| Notes	Grid walking
2021	3	Binary Diagnostic	Prob \| Src \| Notes	Bitwise operations
2021	4	Giant Squid	Prob \| Src \| Notes	Data structures
2021	5	Hydrothermal Venture	Prob \| Src \| Notes	Grid walking
2021	6	Lanternfish	Prob \| Src \| Notes	Dynamic programming
2021	7	The Treachery of Whales	Prob \| Src \| Notes	Mathematics
2021	8	Seven Segment Search	Prob \| Src \| Notes	Constraint satisfaction
2021	9	Smoke Basin	Prob \| Src \| Notes	BFS/DFS
2021	10	Syntax Scoring	Prob \| Src \| Notes	Data structures
2021	11	Dumbo Octopus	Prob \| Src \| Notes	BFS/DFS
2021	12	Passage Pathing	Prob \| Src \| Notes	Memoization
2021	13	Transparent Origami	Prob \| Src \| Notes	GeometryManual inspection
2021	14	Extended Polymerization	Prob \| Src \| Notes	Dynamic programming
2021	15	Chiton	Prob \| Src \| Notes	Dijkstra
2021	16	Packet Decoder	Prob \| Src \| Notes	Parsing
2021	17	Trick Shot	Prob \| Src \| Notes	MathematicsPuzzlePhysics
2021	18	Snailfish	Prob \| Src \| Notes	Data structures
2021	19	Beacon Scanner	Prob \| Src \| Notes	Image processingGeometry
2021	20	Trench Map	Prob \| Src \| Notes	Cellular automata
2021	21	Dirac Dice	Prob \| Src \| Notes	Dynamic programming
2021	22	Reactor Reboot	Prob \| Src \| Notes	Data structuresGeometry
2021	23	Amphipod	Prob \| Src \| Notes	Dijkstra
2021	24	Arithmetic Logic Unit	Prob \| Src \| Notes	VMManual inspectionPuzzle
2021	25	Sea Cucumber	Prob \| Src \| Notes	Cellular automata
2020	1	Report Repair	Prob \| Src \| Notes	Brute forceData structures
2020	2	Password Philosophy	Prob \| Src \| Notes	Brute force
2020	3	Toboggan Trajectory	Prob \| Src \| Notes	Brute force
2020	4	Passport Processing	Prob \| Src \| Notes	String manipulation
2020	5	Binary Boarding	Prob \| Src \| Notes	Puzzle
2020	6	Custom Customs	Prob \| Src \| Notes	Data structures
2020	7	Handy Haversacks	Prob \| Src \| Notes	BFS/DFS
2020	8	Handheld Halting	Prob \| Src \| Notes	VMBrute force
2020	9	Encoding Error	Prob \| Src \| Notes	Memoization
2020	10	Adapter Array	Prob \| Src \| Notes	MemoizationDynamic programming
2020	11	Seating System	Prob \| Src \| Notes	Cellular automata
2020	12	Rain Risk	Prob \| Src \| Notes	GeometryGrid walking
2020	13	Shuttle Search	Prob \| Src \| Notes	Modular arithmetic
2020	14	Docking Data	Prob \| Src \| Notes	Bitwise operations
2020	15	Rambunctious Recitation	Prob \| Src \| Notes	Brute forceData structures
2020	16	Ticket Translation	Prob \| Src \| Notes	Constraint satisfaction
2020	17	Conway Cubes	Prob \| Src \| Notes	Cellular automata
2020	18	Operation Order	Prob \| Src \| Notes	Parsing
2020	19	Monster Messages	Prob \| Src \| Notes	BFS/DFS
2020	20	Jurassic Jigsaw	Prob \| Src \| Notes	Image processingGeometry
2020	21	Allergen Assessment	Prob \| Src \| Notes	Constraint satisfaction
2020	22	Crab Combat	Prob \| Src \| Notes	Data structuresRecursion
2020	23	Crab Cups	Prob \| Src \| Notes	Data structures
2020	24	Lobby Layout	Prob \| Src \| Notes	Cellular automataGrid walking
2020	25	Combo Breaker	Prob \| Src \| Notes	Brute forceModular arithmetic
2019	1	The Tyranny of the Rocket Equation	Prob \| Src \| Notes	Brute force
2019	2	1202 Program Alarm	Prob \| Src \| Notes	IntcodeBrute force
2019	3	Crossed Wires	Prob \| Src \| Notes	Grid walkingCoordinate compression
2019	4	Secure Container	Prob \| Src \| Notes	Brute force
2019	5	Sunny with a Chance of Asteroids	Prob \| Src \| Notes	Intcode
2019	6	Universal Orbit Map	Prob \| Src \| Notes	BFS/DFS
2019	7	Amplification Circuit	Prob \| Src \| Notes	IntcodeBrute force
2019	8	Space Image Format	Prob \| Src \| Notes	Image processingManual inspection
2019	9	Sensor Boost	Prob \| Src \| Notes	Intcode
2019	10	Monitoring Station	Prob \| Src \| Notes	Geometry
2019	11	Space Police	Prob \| Src \| Notes	IntcodeManual inspection
2019	12	The N-Body Problem	Prob \| Src \| Notes	PuzzlePeriod findingPhysics
2019	13	Care Package	Prob \| Src \| Notes	IntcodeArcade game
2019	14	Space Stoichiometry	Prob \| Src \| Notes	RecursionBinary search
2019	15	Oxygen System	Prob \| Src \| Notes	IntcodeBFS/DFSMaze
2019	16	Flawed Frequency Transmission	Prob \| Src \| Notes	PuzzleMemoization
2019	17	Set and Forget	Prob \| Src \| Notes	IntcodeGrid walkingString manipulationManual inspection
2019	18	Many-Worlds Interpretation	Prob \| Src \| Notes	DijkstraMaze
2019	19	Tractor Beam	Prob \| Src \| Notes	IntcodeGeometry
2019	20	Donut Maze	Prob \| Src \| Notes	BFS/DFSMaze
2019	21	Springdroid Adventure	Prob \| Src \| Notes	IntcodePuzzle
2019	22	Slam Shuffle	Prob \| Src \| Notes	MathematicsModular arithmetic
2019	23	Category Six	Prob \| Src \| Notes	Intcode
2019	24	Planet of Discord	Prob \| Src \| Notes	Cellular automata
2019	25	Cryostasis	Prob \| Src \| Notes	IntcodePuzzleManual inspection