feat(rust): add solution for 2024 day 16 part 1

js/src/2024/16/index.js

@@ -0,0 +1,53 @@
+import {
+  Cache,
+  Grid,
+  Orientation,
+  Rotation,
+  astar,
+  dx,
+  dy,
+  normalizeOrientation,
+  solution,
+} from '../../utils/index.js';
+
+const isWall = (point) => point.value === '#';
+
+const parse = (input) => {
+  const maze = Grid.from(input);
+  const start = maze.find((point) => point.value === 'S');
+  const end = maze.find((point) => point.value === 'E');
+  return { maze, start, end };
+};
+
+const speedrun = ({ maze, start, end }) => {
+  const initial = { point: start, facing: Orientation.EAST };
+
+  const hash = (entry) => `${entry.point.label}:${entry.facing}`;
+  const cache = new Cache({ hash });
+
+  const best = astar(initial, null, {
+    cost: (from, to) => (from.point === to.point ? 1000 : 1),
+    done: (current) => current.point === end,
+    nodesFor: ({ point, facing }) => {
+      const nodes = [
+        cache.lookup({ point, facing: normalizeOrientation(facing + Rotation.TURN_RIGHT) }),
+        cache.lookup({ point, facing: normalizeOrientation(facing + Rotation.TURN_LEFT) }),
+      ];
+
+      const forwards = maze.getPoint(point.x + dx(facing), point.y + dy(facing));
+      if (forwards && !isWall(forwards)) {
+        nodes.push(cache.lookup({ point: forwards, facing }));
+      }
+      return nodes;
+    },
+  });
+
+  return best;
+};
+
+export const partOne = solution((input) => {
+  const { maze, start, end } = parse(input);
+  return speedrun({ method: astar, maze, start, end }).score;
+});
+
+// TODO: Part two requires signficant changes to generic bfs implementation: later ;)

puzzles/2024/16/examples.yaml

@@ -0,0 +1,45 @@
+part-one:
+  - input: &example1 |
+      ###############
+      #.......#....E#
+      #.#.###.#.###.#
+      #.....#.#...#.#
+      #.###.#####.#.#
+      #.#.#.......#.#
+      #.#.#####.###.#
+      #...........#.#
+      ###.#.#####.#.#
+      #...#.....#.#.#
+      #.#.#.###.#.#.#
+      #.....#...#.#.#
+      #.###.#.#.#.#.#
+      #S..#.....#...#
+      ###############
+    answer: 7036
+
+  - input: &example2 |
+      #################
+      #...#...#...#..E#
+      #.#.#.#.#.#.#.#.#
+      #.#.#.#...#...#.#
+      #.#.#.#.###.#.#.#
+      #...#.#.#.....#.#
+      #.#.#.#.#.#####.#
+      #.#...#.#.#.....#
+      #.#.#####.#.###.#
+      #.#.#.......#...#
+      #.#.###.#####.###
+      #.#.#...#.....#.#
+      #.#.#.#####.###.#
+      #.#.#.........#.#
+      #.#.#.#########.#
+      #S#.............#
+      #################
+    answer: 11048
+
+part-two:
+  - input: *example1
+    answer: 45
+
+  - input: *example2
+    answer: 64