From 26d5edcf003ce8ca6e905581b4422ba37fd5f272 Mon Sep 17 00:00:00 2001
From: Mark Fulton <mfulton26@gmail.com>
Date: Tue, 17 Dec 2024 07:20:09 -0600
Subject: [PATCH] feat: 2024 Day 15 Part 1

---
 2024/day/15/part/1/solve.test.ts | 46 ++++++++++++++++++++++++++++++++
 2024/day/15/part/1/solve.ts      | 34 +++++++++++++++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 2024/day/15/part/1/solve.test.ts
 create mode 100644 2024/day/15/part/1/solve.ts

diff --git a/2024/day/15/part/1/solve.test.ts b/2024/day/15/part/1/solve.test.ts
new file mode 100644
index 0000000..6e97feb
--- /dev/null
+++ b/2024/day/15/part/1/solve.test.ts
@@ -0,0 +1,46 @@
+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("smaller example", () => {
+  const input = `\
+########
+#..O.O.#
+##@.O..#
+#...O..#
+#.#.O..#
+#...O..#
+#......#
+########
+
+<^^>>>vv<v>>v<<`;
+
+  assertEquals(solve(input), 2028);
+});
+
+Deno.test("large example", () => {
+  const input = `\
+##########
+#..O..O.O#
+#......O.#
+#.OO..O.O#
+#..O@..O.#
+#O#..O...#
+#O..O..O.#
+#.OO.O.OO#
+#....O...#
+##########
+
+<vv>^<v^>v>^vv^v>v<>v^v<v<^vv<<<^><<><>>v<vvv<>^v^>^<<<><<v<<<v^vv^v>^
+vvv<<^>^v^^><<>>><>^<<><^vv^^<>vvv<>><^^v>^>vv<>v<<<<v<^v>^<^^>>>^<v<v
+><>vv>v^v^<>><>>>><^^>vv>v<^^^>>v^v^<^^>v^^>v^<^v>v<>>v^v^<v>v^^<^^vv<
+<<v<^>>^^^^>>>v^<>vvv^><v<<<>^^^vv^<vvv>^>v<^^^^v<>^>vvvv><>>v^<<^^^^^
+^><^><>>><>^^<<^^v>>><^<v>^<vv>>v>>>^v><>^v><<<<v>>v<v<v>vvv>^<><<>^><
+^>><>^v<><^vvv<^^<><v<<<<<><^v<<<><<<^^<v<^^^><^>>^<v^><<<^>>^v<v^v<v^
+>^>>^v>vv>^<<^v<>><<><<v<<v><>v<^vv<<<>^^v^>^^>>><<^v>>v^v><^^>>^<>vv^
+<><^^>^^^<><vvvvv^v<v<<>^v<v>v<<^><<><<><<<^^<<<^<<>><<><^^^>^^<>^>v<>
+^^>vv<^v^v<vv>^<><v<^v>^^^>>>^^vvv^>vvv<>>>^<^>>>>>^<<^v>^vvv<>^<><<v>
+v^^>>><<^^<>>^v^<v^vv<>v^<<>^<^v^v><^<<<><<^<v><v<>vv>>v><v^<vv<>v^<<^`;
+
+  assertEquals(solve(input), 10092);
+});
diff --git a/2024/day/15/part/1/solve.ts b/2024/day/15/part/1/solve.ts
new file mode 100644
index 0000000..7c8846d
--- /dev/null
+++ b/2024/day/15/part/1/solve.ts
@@ -0,0 +1,34 @@
+const moveToDir = { "^": [0, -1], "v": [0, 1], "<": [-1, 0], ">": [1, 0] };
+
+export default function solve(input: string) {
+  const [top, bottom] = input.split("\n\n");
+  const grid = top.split("\n").map((line) => [...line]);
+  const moves = bottom.replaceAll("\n", "");
+  let py = grid.findIndex((row) => row.includes("@")),
+    px = grid[py].indexOf("@");
+  function swap(x1: number, y1: number, x2: number, y2: number) {
+    [grid[y1][x1], grid[y2][x2]] = [grid[y2][x2], grid[y1][x1]];
+  }
+  for (const move of moves) {
+    const [dx, dy] = moveToDir[move as keyof typeof moveToDir];
+    let canMove = false, [wx, wy] = [px + dx, py + dy];
+    while (grid[wy][wx] !== "#") {
+      canMove ||= grid[wy][wx] === ".", wx += dx, wy += dy;
+    }
+    if (!canMove) continue;
+    let d = 0;
+    while (grid[py + (d + 1) * dy][px + (d + 1) * dx] !== ".") d++;
+    for (; d; d--) {
+      swap(px + d * dx, py + d * dy, px + (d + 1) * dx, py + (d + 1) * dy);
+    }
+    swap(px, py, px + dx, py + dy);
+    px += dx, py += dy;
+  }
+  let sum = 0;
+  for (let y = 0; y < grid.length; y++) {
+    for (let x = 0; x < grid[y].length; x++) {
+      if (grid[y][x] === "O") sum += 100 * y + x;
+    }
+  }
+  return sum;
+}