Day 6 & 7

2024/06/index.ts

@@ -0,0 +1,134 @@
+const fs = require('fs');
+
+const input = fs.readFileSync(__dirname + '/input.txt', 'utf8');
+
+interface Coord { x: number, y: number };
+enum Dir {
+    Up,
+    Right,
+    Down,
+    Left
+}
+
+const obs: Array<Coord> = [];
+let guard: { pos: Coord, dir: Dir } = { pos: { x: 0, y: 0}, dir: Dir.Up };
+
+const keyMap: { [key: string]: (pos: Coord) => any } = {
+    "#": (pos: Coord) => obs.push(pos),
+    "^": (pos: Coord) => guard = { pos, dir: Dir.Up },
+    ">": (pos: Coord) => guard = { pos, dir: Dir.Up },
+    "v": (pos: Coord) => guard = { pos, dir: Dir.Up },
+    "<": (pos: Coord) => guard = { pos, dir: Dir.Up },
+}
+
+let x = 0;
+let y = 0;
+for (let i = 0; i <= input.length; i++) {
+    const char = input[i];
+    if (char === "\n") {
+        y++;
+        x = 0;
+        continue;
+    }
+    if (keyMap[char]) {
+        keyMap[char]({ x, y });
+    }
+    x++;
+}
+const width = x + 1;
+const height = y + 1;
+const guardStart = guard.pos;
+
+
+const positions: Array<Coord> = [guard.pos];
+
+function coodsMatch(a: Coord, b: Coord) {
+    return a.x === b.x && a.y === b.y;
+}
+
+function getNextPosition() {
+    if (guard.dir === Dir.Up) {
+        return { x: guard.pos.x, y: guard.pos.y - 1 };
+    }
+    if (guard.dir === Dir.Right) {
+        return { x: guard.pos.x + 1, y: guard.pos.y };
+    }
+    if (guard.dir === Dir.Down) {
+        return { x: guard.pos.x, y: guard.pos.y + 1 };
+    }
+    return { x: guard.pos.x - 1, y: guard.pos.y };
+}
+
+function rotateGuard() {
+    if (guard.dir === Dir.Up) {
+        guard.dir = Dir.Right;
+    } else if (guard.dir === Dir.Right) {
+        guard.dir = Dir.Down;
+    } else if (guard.dir === Dir.Down) {
+        guard.dir = Dir.Left;
+    } else {
+        guard.dir = Dir.Up;
+    }
+}
+
+function isObs(coord: Coord, otherObs: Array<Coord>|null = null) {
+    return (otherObs || obs).some((obsCoord) => coodsMatch(obsCoord, coord));
+}
+
+function offMap(coord: Coord) {
+    return coord.x >= width
+        || coord.x < 0
+        || coord.y >= height
+        || coord.y < 0;
+}
+
+function alreadyVisited(coord: Coord) {
+    return positions.some((pos) => coodsMatch(pos, coord));
+}
+
+while (true) {
+    const nextPos = getNextPosition();
+    if (isObs(nextPos)) {
+        rotateGuard();
+        continue;
+    }
+    if (offMap(nextPos)) {
+        break;
+    }
+    guard.pos = nextPos;
+    if (!alreadyVisited(nextPos)) {
+        positions.push(nextPos);
+    }
+}
+
+// Part 2
+let loops = 0;
+positions.slice(1).forEach((pos, i) => {
+    console.log(Math.floor(`${i / positions.length * 100}%`));
+    guard.pos = guardStart;
+    guard.dir = Dir.Up;
+    const newObs = [...obs, pos];
+    const guardPositions: Array<string> = [];
+    while (true) {
+        const nextPos = getNextPosition();
+        if (isObs(nextPos, newObs)) {
+            rotateGuard();
+            continue;
+        }
+        if (offMap(nextPos)) {
+            break;
+        }
+        const guardPos = `${guard.pos.x},${guard.pos.y},${guard.dir}`;
+        if (guardPositions.includes(guardPos)) {
+            loops++;
+            break;
+        }
+        guardPositions.push(guardPos);
+        guard.pos = nextPos;
+    }
+    x++;
+});
+// End Part 2
+
+console.log(positions.length);
+console.log(loops);