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Documentation Index

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Advent of Code 2018 is a complete year — all 25 days solved, both parts. The year follows the Elves through time-travel mishaps featuring fabric-claim disputes, guard-sleep schedules, marble games, mine-cart collisions, Elf combat, and a register-based virtual machine. Day 1 Part 2 and Day 19 Part 1 both earned global leaderboard scores. Nearly every solution carries a full test suite.

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Progress

DayTitlePart 1Part 2Tests
01Chronal Calibration⭐⭐✅
02Inventory Management System⭐⭐✅
03No Matter How You Slice It⭐⭐✅
04Repose Record⭐⭐✅
05Alchemical Reduction⭐⭐✅
06Chronal Coordinates⭐⭐✅
07The Sum of Its Parts⭐⭐✅
08Memory Maneuver⭐⭐✅
09Marble Mania⭐⭐✅
10The Stars Align⭐⭐✅
11Chronal Charge⭐⭐✅
12Subterranean Sustainability⭐⭐✅
13Mine Cart Madness⭐⭐✅
14Chocolate Charts⭐⭐✅
15Beverage Bandits⭐⭐✅
16Chronal Classification⭐⭐✅
17Reservoir Research⭐⭐✅
18Settlers of The North Pole⭐⭐✅
19Go With The Flow⭐⭐✅
20A Regular Map⭐⭐✅
21Chronal Conversion⭐⭐❓
22Mode Maze⭐⭐✅
23Experimental Emergency Teleportation⭐⭐✅
24Immune System Simulator 20XX⭐⭐✅
25Four-Dimensional Adventure⭐⭐✅

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Notable Solutions

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Day 15 — Beverage Bandits

One of the most demanding puzzles of 2018: a full combat simulation between Elves and Goblins on a cave grid. Units take turns in reading order (top-to-bottom, left-to-right), each moving one step toward the nearest reachable enemy (BFS with tie-breaking) and then attacking the adjacent enemy with the lowest hit points. Part 2 binary-searches for the minimum Elf attack power that lets the Elves win without any casualties. The solution uses a MoveNode tree to reconstruct movement paths from BFS.

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Day 11 — Chronal Charge

Part 1 finds the 3×3 sub-grid with the highest total power level by brute-force summation. Part 2 asks for the best sub-grid of any size from 1×1 to 300×300. The efficient solution uses a summed-area table (prefix sums) so that any rectangular region’s sum can be computed in O(1), reducing the full search from O(n⁵) to O(n³).

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Day 18 — Settlers of The North Pole

A classic cellular automaton on a grid of open ground (.), trees (|), and lumberyards (#). Each cell’s next state depends on its eight neighbours. Part 1 runs 10 minutes. Part 2 runs 1,000,000,000 minutes — solved by detecting the cycle length in the sequence of states and skipping ahead, then running just the remaining steps.
Puzzle inputs are personal and are not stored in this repository. Solutions fetch input at runtime using aocd (aocd.data).

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