Solutions for Advent of Code 2023, written in Rust.
| Day | Name | Description | Strategy | Run time* |
|---|---|---|---|---|
| 1 | Trebuchet?! | Find first and last number words | RegEx & HashMap | 4 ms |
| 2 | Cube Conundrum | Red, green, blue cube selection game | Nom parse, partial order on RGB triples | 1 ms |
| 3 | Gear Ratios | Numbers and symbols in a grid | Row-major scan with look-around | 2 ms |
| 4 | Scratchcards | Winning numbers win more cards | Set intersection & 1-pass array scan | 3 ms |
| 5 | Fertilizer | Follow range-to-range mappings | Range intersection via sort/merge join | 2 ms |
| 6 | Wait For It | Calculate optimal toy button press | Quadratic roots formula | 1 ms |
| 7 | Camel Cards | Rank hands by strength then cards | Custom total order, joker plays as mode card | 2 ms |
| 8 | Haunted Wasteland | Simultaneous graph traversal | Cycle finding, least common multiple of path length | 11 ms |
| 9 | Mirage Maintenance | Triangular sequence extension | Reverse lines for part 2 | 2 ms |
| 10 | Pipe Maze | Traverse loop of pipe in a grid | Observe neighbouring pipes to find ways available | 4 ms |
| 11 | Cosmic Expansion | Expand space between galaxies | Sparse 2D grid with HashSet | 1 ms |
| 12 | Hot Springs | Damaged spring pattern matching | Recursive DP, fast FxHashMap memoization | 31 ms |
| 13 | Point of Incidence | Find reflections in landscape | Simple comparisons with short-circuiting | 2 ms |
| 14 | Parabolic Reflector Dish | Roll rocks around a grid | Find a cycle in the state and extrapolate | 60 ms |
| 15 | Lens Library | Implement a HashMap | As given | 2 ms |
| 16 | The Floor Will Be Lava | Shine a beam through grid of mirrors | Depth-first search | 23 ms |
| 17 | Clumsy Crucible | Minimize loss along a path with restricted movement | Dijkstra's shortest path with modifications | 350 ms |
| 18 | Lavaduct Lagoon | Calculate lagoon area from movement instructions | Shoelace formula for polygon area, plus perimeter | 1 ms |
| 19 | Aplenty | Filter parts through interconnected workflows | Model workflows with range intersection | 3 ms |
| 20 | Pulse Propagation | Calculate pulses sent after pushing a button | Model system and find cycles in the state | 20 ms |
| 21 | Step Counter | Count walks in an infinitely-repeating garden | Fit a quadratic equation to specially-crafted input | 1,100 ms |
| 22 | Sand Slabs | Determine falling bricks in a stack | Process bricks bottom-up tracking a 2D height map | 40 ms |
| 23 | A Long Walk | Find longest walk in a grid (part 2 with cycles) | Reduce to junction graph, exhaustive DFS with PetGraph | 810 ms |
| 24 | Never Tell Me The Odds | Calculate intersection of hailstone paths | Solve system of quadratic equations with Z3 | 95 ms |
| 25 | Snowverload | Cut 3 wires to divide a system in two | Parallel randomized Karger's algorithm | ~300 ms |
*Rough wall clock time on my PC, single-threaded except for Day 25
(--release mode, directly executed, not via Cargo)