feat(js): add solutions for 2024 day 20 part 1

js/src/2024/20/index.js

@@ -0,0 +1,51 @@
+import { Grid, astar, solution } from '../../utils/index.js';
+
+const WALL = '#';
+
+const isPassable = (point) => point.value !== WALL;
+
+const directions = ['up', 'down', 'left', 'right'];
+
+const parse = (input) => {
+  const track = Grid.from(input);
+  const start = track.find((point) => point.value === 'S');
+  const end = track.find((point) => point.value === 'E');
+  return { track, start, end };
+};
+
+const traverse = ({ start, end }) => {
+  const result = astar(start, null, {
+    done: (current) => current === end,
+    neighborsFor: (current) => current.adjacentNeighbors.filter(isPassable),
+  });
+  return result;
+};
+
+export const partOne = solution.inefficient((input, { minSavings = 100 }) => {
+  const { start, end } = parse(input);
+
+  const honest = traverse({ start, end });
+  const target = honest.score - minSavings;
+
+  let count = 0;
+  for (const enter of honest.path) {
+    for (const dir of directions) {
+      const phase = enter[dir];
+      if (!phase || isPassable(phase)) continue;
+
+      const exit = phase[dir];
+      if (!exit || !isPassable(exit)) continue;
+
+      const first = traverse({ start, end: enter });
+      const second = traverse({ start: exit, end });
+      const score = first.score + 2 + second.score;
+
+      if (score <= target) {
+        ++count;
+      }
+    }
+  }
+  return count;
+});
+
+// TODO: Ain't nobody got time for part two ;)

puzzles/2024/20/examples.yaml

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+part-one:
+  - input: |
+      ###############
+      #...#...#.....#
+      #.#.#.#.#.###.#
+      #S#...#.#.#...#
+      #######.#.#.###
+      #######.#.#...#
+      #######.#.###.#
+      ###..E#...#...#
+      ###.#######.###
+      #...###...#...#
+      #.#####.#.###.#
+      #.#...#.#.#...#
+      #.#.#.#.#.#.###
+      #...#...#...###
+      ###############
+    answer: 4
+    args:
+      min-savings: 30