day: ⭐ Day 6, 2024 (part 1)

.env.example

@@ -1,2 +1,2 @@
 AOC_SESSION=sessionCookie
-GITHUB_REPO=username/repo
+REPO=username/repo

.lume/lib/data.ts

@@ -4,7 +4,7 @@ import { Calendar } from "./types.ts";
 
 const root = Deno.cwd();
 const yearRegex = /^\d{4}$/;
-const repositoryUrl = "https://github.com/" + Deno.env.get("GITHUB_REPO");
+const repositoryUrl = "https://github.com/" + Deno.env.get("REPO");
 
 const calendars: Calendar[] = [];
 for (const dir of Deno.readDirSync(root)) {

2024/6_guard-gallivant/part-1.ts

@@ -0,0 +1,69 @@
+// Read the input file and split it into lines
+const input = await Deno.readTextFile("./input.txt");
+const grid = input.split("\n").map((line) => line.split(""));
+
+// the guard is the first of any of the following characters: ^, v, <, >
+const guard = grid
+  .map((row) => row.find((cell) => "^v<>".includes(cell)))
+  .find((cell) => cell);
+
+if (!guard) {
+  throw new Error("No guard found");
+}
+
+let guardPosition = {
+  x: grid.findIndex((row) => row.includes(guard)),
+  y: grid[grid.findIndex((row) => row.includes(guard))].indexOf(guard),
+};
+
+const moveGuard = (position: { x: number; y: number }) => {
+  const nextPosition = { ...position };
+  const direction = grid[position.x][position.y]; // ^, v, <, >
+
+  const nextPositionOutOfBounds = nextPosition.x < 0 ||
+    nextPosition.x >= grid.length ||
+    nextPosition.y < 0 ||
+    nextPosition.y >= grid[0].length;
+
+  if (direction === "^") {
+    nextPosition.x--;
+  } else if (direction === "v") {
+    nextPosition.x++;
+  } else if (direction === "<") {
+    nextPosition.y--;
+  } else if (direction === ">") {
+    nextPosition.y++;
+  }
+
+  // check if the next position is a wall
+  if (
+    !nextPositionOutOfBounds &&
+    grid[nextPosition.x][nextPosition.y] === "#"
+  ) {
+    // rotate the guard 90 degrees to the right
+    const directions = ["^", ">", "v", "<"];
+    const currentIndex = directions.indexOf(direction);
+    const nextIndex = (currentIndex + 1) % directions.length;
+    grid[position.x][position.y] = directions[nextIndex];
+  } else {
+    // move the guard
+    grid[nextPosition.x][nextPosition.y] = direction;
+    grid[position.x][position.y] = "X";
+    guardPosition = { ...nextPosition };
+  }
+};
+
+const isGuardInsideBounds = () =>
+  grid.some((row) => row.includes("^")) ||
+  grid.some((row) => row.includes("v")) ||
+  grid.some((row) => row.includes("<")) ||
+  grid.some((row) => row.includes(">"));
+
+while (isGuardInsideBounds()) {
+  moveGuard(guardPosition);
+}
+
+// count the number of cells visited by the guard
+const visitedCells = grid.flat().filter((cell) => cell === "X");
+
+console.log(visitedCells.length);