feat(js): add solutions for 2023 day 8

js/src/2023/08/index.js

@@ -0,0 +1,67 @@
+import { Graph, lcm, solution } from '../../utils';
+
+const PATH_MATCHER = /(\w+) = \((\w+), (\w+)\)/g;
+
+const parse = (input) => {
+  const parts = input.trim().split('\n\n');
+
+  const instructions = parts[0].split('').map((i) => (i === 'L' ? 0 : 1));
+
+  const network = new Graph();
+  for (const [_, from, a, b] of parts[1].matchAll(PATH_MATCHER)) {
+    network.edge(from, a);
+    network.edge(from, b);
+  }
+
+  return { instructions, network };
+};
+
+export const partOne = solution((input) => {
+  const { network, instructions } = parse(input);
+
+  const start = network.find('AAA');
+  const goal = network.find('ZZZ');
+
+  let current = start;
+  let steps = 0;
+  while (current !== goal) {
+    const move = instructions[steps % instructions.length];
+    const next = current.edges[move] || current.edges[0];
+    current = next.to;
+    ++steps;
+  }
+
+  return steps;
+});
+
+export const partTwo = solution((input) => {
+  const { network, instructions } = parse(input);
+
+  const starts = network.vertices.filter((v) => v.value.endsWith('A'));
+  const atGoal = (ghost) => ghost.current.value.endsWith('Z');
+  const hasCycle = (ghost) => ghost.cycle && ghost.cycle.length;
+
+  const ghosts = starts.map((start) => ({
+    current: start,
+    cycle: null,
+  }));
+  let steps = 0;
+  while (!ghosts.every(hasCycle)) {
+    const move = instructions[steps % instructions.length];
+    for (const ghost of ghosts) {
+      const next = ghost.current.edges[move] || ghost.current.edges[0];
+      ghost.current = next.to;
+      if (atGoal(ghost)) {
+        if (!ghost.cycle) {
+          ghost.cycle = { start: steps };
+        } else if (!ghost.cycle.length) {
+          ghost.cycle.length = steps - ghost.cycle.start;
+        }
+      }
+    }
+    ++steps;
+  }
+
+  // We meet again AoC 2022 day 11! :o
+  return lcm(ghosts.map((ghost) => ghost.cycle.length));
+});

puzzles/2023/08/examples.yaml

@@ -0,0 +1,34 @@
+part-one:
+  - input: |
+      RL
+
+      AAA = (BBB, CCC)
+      BBB = (DDD, EEE)
+      CCC = (ZZZ, GGG)
+      DDD = (DDD, DDD)
+      EEE = (EEE, EEE)
+      GGG = (GGG, GGG)
+      ZZZ = (ZZZ, ZZZ)
+    answer: 2
+
+  - input: |
+      LLR
+
+      AAA = (BBB, BBB)
+      BBB = (AAA, ZZZ)
+      ZZZ = (ZZZ, ZZZ)
+    answer: 6
+
+part-two:
+  - input: |
+      LR
+
+      11A = (11B, XXX)
+      11B = (XXX, 11Z)
+      11Z = (11B, XXX)
+      22A = (22B, XXX)
+      22B = (22C, 22C)
+      22C = (22Z, 22Z)
+      22Z = (22B, 22B)
+      XXX = (XXX, XXX)
+    answer: 6