feat(js): add solutions for 2024 day 14

js/src/2024/14/index.js

@@ -0,0 +1,75 @@
+/* eslint-disable no-loop-func */
+
+import { mod, multiply, solution } from '../../utils/index.js';
+
+const SIGNED_NUMBER_MATCHER = /-?\d+/g;
+
+const parse = (input) =>
+  input
+    .trim()
+    .split('\n')
+    .map((line) => {
+      const [px, py, dx, dy] = Array.from(line.matchAll(SIGNED_NUMBER_MATCHER)).map((match) =>
+        Number(match[0]),
+      );
+      return { px, py, dx, dy };
+    });
+
+const predict = (robot, steps, width, height) => {
+  const px = mod(robot.px + steps * robot.dx, width);
+  const py = mod(robot.py + steps * robot.dy, height);
+  return { px, py };
+};
+
+// Whether given robot is within radial distance 1 of other robot
+const isNearOther = (robot, other) => {
+  const diffx = Math.abs(robot.px - other.px);
+  const diffy = Math.abs(robot.py - other.py);
+  return robot !== other && diffx <= 1 && diffy <= 1;
+};
+
+// Whether this configuration of robots visually contains a hidden Christmas tree (!)
+// Note: uses an arbitrary cluster threshold, as Erik sneakily decided to not let _all_ robots contribute
+const isChristmasTree = (robots, threshold = 0.75) => {
+  const total = robots.length;
+  const clustered = robots.reduce((sum, robot) => sum + robots.some((other) => isNearOther(robot, other)), 0);
+  const percent = clustered / total;
+  return percent >= threshold;
+};
+
+export const partOne = solution((input, { width = 101, height = 103 }) => {
+  const robots = parse(input);
+
+  const middlex = (width / 2) | 0;
+  const middley = (height / 2) | 0;
+
+  const steps = 100;
+
+  const quadrants = [0, 0, 0, 0];
+
+  for (const robot of robots) {
+    const { px, py } = predict(robot, steps, width, height);
+    const inMiddle = px === middlex || py === middley;
+    if (!inMiddle) {
+      const index = ((((py - 1) / middley) | 0) << 1) | (((px - 1) / middlex) | 0);
+      quadrants[index]++;
+    }
+  }
+
+  return multiply(quadrants);
+});
+
+export const partTwo = solution.inefficient((input, { width = 101, height = 103 }) => {
+  const robots = parse(input);
+
+  let steps = 1;
+  while (true) {
+    const snapshot = robots.map((robot) => predict(robot, steps, width, height));
+    if (isChristmasTree(snapshot)) {
+      break;
+    }
+    ++steps;
+  }
+
+  return steps;
+});

puzzles/2024/14/examples.yaml

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+part-one:
+  - input: |
+      p=0,4 v=3,-3
+      p=6,3 v=-1,-3
+      p=10,3 v=-1,2
+      p=2,0 v=2,-1
+      p=0,0 v=1,3
+      p=3,0 v=-2,-2
+      p=7,6 v=-1,-3
+      p=3,0 v=-1,-2
+      p=9,3 v=2,3
+      p=7,3 v=-1,2
+      p=2,4 v=2,-3
+      p=9,5 v=-3,-3
+    answer: 12
+    args:
+      width: 11
+      height: 7