feat: 2022 Day 17

Author: mfulton26

2022/day/17/part/1/solve.ts

@@ -8,10 +8,10 @@ const shapes = [
 
 const pushCharToDirection: Record<string, number> = { "<": -1, ">": 1 };
 
-export default function solve(input: string) {
+export default function solve(input: string, { rocks = 2022 } = {}) {
   const chamber: boolean[][] = [];
-  for (let i = 0, j = 0; i < 2022; i++) {
-    const shape = shapes[i % shapes.length];
+  for (let rock = 0, j = 0; rock < rocks; rock++) {
+    const shape = shapes[rock % shapes.length];
     for (let x = 2, y = chamber.length + 3; y >= 0; y--) {
       const dx = pushCharToDirection[input[j++ % input.length]];
       if (

2022/day/17/part/2/solve.test.ts

@@ -0,0 +1,9 @@
+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("example", () => {
+  const input = ">>><<><>><<<>><>>><<<>>><<<><<<>><>><<>>";
+
+  assertEquals(solve(input), 1514285714288);
+});

2022/day/17/part/2/solve.ts

@@ -0,0 +1,60 @@
+const shapes = [
+  Object.assign([[0, 0], [1, 0], [2, 0], [3, 0]], { width: 4 }),
+  Object.assign([[1, 0], [0, 1], [1, 1], [2, 1], [1, 2]], { width: 3 }),
+  Object.assign([[0, 0], [1, 0], [2, 0], [2, 1], [2, 2]], { width: 3 }),
+  Object.assign([[0, 0], [0, 1], [0, 2], [0, 3]], { width: 1 }),
+  Object.assign([[0, 0], [1, 0], [0, 1], [1, 1]], { width: 2 }),
+];
+
+const pushCharToDirection: Record<string, number> = { "<": -1, ">": 1 };
+
+function stringify(chamber: boolean[][]) {
+  let result = "";
+  for (let i = chamber.length - 1; i >= 0; i--) {
+    for (const item of chamber[i]) result += item ? "#" : ".";
+    result += "\n";
+  }
+  return result;
+}
+
+export default function solve(input: string, { rocks = 1000000000000 } = {}) {
+  const chamber: boolean[][] = [];
+  let atFirstRepeat:
+    | { rock: number; height: number; secondRepeatRegExp: RegExp }
+    | undefined;
+  let skippedHeight = 0;
+  for (let rock = 1, i = 0, j = 0; rock <= rocks; rock++, i++) {
+    const shape = shapes[i % shapes.length];
+    for (let x = 2, y = chamber.length + 3; y >= 0; y--) {
+      const dx = pushCharToDirection[input[j++ % input.length]];
+      if (
+        x + dx >= 0 && x + dx + shape.width <= 7 &&
+        !shape.some(([rx, ry]) => chamber[y + ry]?.[x + rx + dx])
+      ) x += dx;
+      if (y === 0 || shape.some(([rx, ry]) => chamber[y + ry - 1]?.[x + rx])) {
+        for (const [rx, ry] of shape) {
+          chamber[y + ry] ??= Array.from({ length: 7 }, () => false);
+          chamber[y + ry][x + rx] = true;
+        }
+        break;
+      }
+    }
+    if (skippedHeight) continue;
+    if (rock < 10000) continue;
+    if (!atFirstRepeat) {
+      const match = /((?:[.#]{7}\n){40,}?)(\1+)/m.exec(stringify(chamber));
+      if (match === null) continue;
+      const [, lines, repeats] = match;
+      const times = repeats.length / lines.length;
+      const secondRepeatRegExp = new RegExp(`(?:${lines}){${times + 2}}`, "m");
+      atFirstRepeat = { rock, height: chamber.length, secondRepeatRegExp };
+    } else if (atFirstRepeat.secondRepeatRegExp.test(stringify(chamber))) {
+      const repeatedRocks = rock - atFirstRepeat.rock;
+      const repeatedHeight = chamber.length - atFirstRepeat.height;
+      const toRepeat = Math.floor((rocks - rock) / repeatedRocks);
+      rock += toRepeat * repeatedRocks;
+      skippedHeight = toRepeat * repeatedHeight;
+    }
+  }
+  return chamber.length + skippedHeight;
+}