feat: 2024 Day 14

Author: mfulton26

2024/day/14/part/1/solve.test.ts

@@ -0,0 +1,21 @@
+import solve from "./solve.ts";
+
+import { assertEquals } from "../../../../../lib/testing/asserts.ts";
+
+Deno.test("example", () => {
+  const 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`;
+
+  assertEquals(solve(input, { width: 11, height: 7 }), 12);
+});

2024/day/14/part/1/solve.ts

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+const regExp = /^p=(?<px>\d+),(?<py>\d+) v=(?<vx>-?\d+),(?<vy>-?\d+)$/gm;
+
+export default function solve(
+  input: string,
+  { width = 101, height = 103, t = 100 } = {},
+) {
+  const robots = input.matchAll(regExp).map((match) => match.map(Number))
+    .map(([, px, py, vx, vy]) => ({ px, py, vx, vy })).toArray();
+  const mid = { x: (width - 1) / 2, y: (height - 1) / 2 };
+  const quadrantCounts = [0, 0, 0, 0];
+  for (const { px, py, vx, vy } of robots) {
+    const fx = mod(px + t * vx, width), fy = mod(py + t * vy, height);
+    if (fx === mid.x || fy === mid.y) continue;
+    quadrantCounts[(fy < mid.y ? 0 : 2) + (fx < mid.x ? 0 : 1)]++;
+  }
+  return quadrantCounts.reduce((product, count) => product * count, 1);
+}
+
+function mod(a: number, b: number) {
+  return ((a % b) + b) % b;
+}

2024/day/14/part/2/solve.test.ts

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+import solve from "./solve.ts";
+
+import { assertEquals } from "../../../../../lib/testing/asserts.ts";
+
+Deno.test("example", () => {
+  const 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`;
+
+  assertEquals(solve(input, { width: 11, height: 7 }), 12);
+});

2024/day/14/part/2/solve.ts

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+const regExp = /^p=(?<px>\d+),(?<py>\d+) v=(?<vx>-?\d+),(?<vy>-?\d+)$/gm;
+
+export default function solve(
+  input: string,
+  { width = 101, height = 103 } = {},
+) {
+  const robots = input.matchAll(regExp).map((match) => match.map(Number))
+    .map(([, px, py, vx, vy]) => ({ px, py, vx, vy })).toArray();
+  moments: for (let t = 0;; t++) {
+    const positionHashes = new Set();
+    for (const { px, py, vx, vy } of robots) {
+      const x = mod(px + vx * t, width), y = mod(py + vy * t, height);
+      const positionHash = `${x},${y}`;
+      if (positionHashes.has(positionHash)) continue moments;
+      positionHashes.add(positionHash);
+    }
+    return t;
+  }
+}
+
+function mod(a: number, b: number) {
+  return ((a % b) + b) % b;
+}