Day 09

deno.json

@@ -32,6 +32,7 @@
     "Day05": "cd ./src/05_SupplyStacks && deno run --allow-read=./input.txt SupplyStacks.ts",
     "Day06": "cd ./src/06_TuningTrouble && deno run --allow-read=./input.txt TuningTrouble.ts",
     "Day07": "cd ./src/07_NoSpaceLeftOnDevice && deno run --allow-read=./input.txt NoSpaceLeftOnDevice.ts",
-    "Day08": "cd ./src/08_TreetopTreeHouse && deno run --allow-read=./input.txt TreetopTreeHouse.ts"
+    "Day08": "cd ./src/08_TreetopTreeHouse && deno run --allow-read=./input.txt TreetopTreeHouse.ts",
+    "Day09": "cd ./src/09_RopeBridge && deno run --allow-read=./input.txt RopeBridge.ts"
   }
 }

src/09_RopeBridge/RopeBridge.ts

@@ -0,0 +1,116 @@
+const input = Deno.readTextFileSync('./input.txt').trimEnd().split('\n');
+
+type Position = {
+  x: number;
+  y: number;
+};
+
+type Instruction = {
+  direction: 'U' | 'D' | 'L' | 'R';
+  amount: number;
+};
+
+function encode(position: Position): string {
+  return `${position.x},${position.y}`;
+}
+
+function makeRope(length = 2): Position[] {
+  const rope: Position[] = [];
+  for (let i = 0; i < Math.max(length, 1); i++) {
+    rope.push({
+      x: 0,
+      y: 0,
+    });
+  }
+  return rope;
+}
+
+function moveRope(instructions: Instruction[], rope: Position[], visitedPositions: Set<string>) {
+  for (const instruction of instructions) {
+    for (let count = 0; count < instruction.amount; count++) {
+      if (instruction.direction === 'U') {
+        rope[0].y++;
+      } else if (instruction.direction === 'D') {
+        rope[0].y--;
+      } else if (instruction.direction === 'L') {
+        rope[0].x--;
+      } else rope[0].x++;
+
+      for (let i = 1; i < rope.length; i++) {
+        const head = rope[i - 1];
+        const tail = rope[i];
+        if (Math.abs(head.x - tail.x) > 1) {
+          if (head.y !== tail.y) {
+            (head.y > tail.y) ? tail.y++ : tail.y--;
+          }
+          if (head.x > tail.x) {
+            tail.x++;
+          } else tail.x--;
+        } else if (Math.abs(head.y - tail.y) > 1) {
+          if (head.x !== tail.x) {
+            (head.x > tail.x) ? tail.x++ : tail.x--;
+          }
+          if (head.y > tail.y) {
+            tail.y++;
+          } else tail.y--;
+        }
+      }
+      visitedPositions.add(encode(rope.at(-1)!));
+    }
+  }
+}
+
+export function printMap(rope: Position[], padding = 5) {
+  if (rope.length < 1) {
+    console.log('Empty Rope');
+    return;
+  }
+
+  const coords: [number[], number[]] = [[], []];
+  rope.forEach((knot) => {
+    coords[0].push(knot.x);
+    coords[1].push(knot.y);
+  });
+  const bounds = {
+    minX: Math.min(...coords[0]) - padding,
+    maxX: Math.max(...coords[0]) + padding + 1,
+    minY: Math.min(...coords[1]) - padding,
+    maxY: Math.max(...coords[1]) + padding + 1,
+  };
+  const width = bounds.maxX - bounds.minX;
+  const height = bounds.maxY - bounds.minY;
+
+  const map: Array<string[]> = [];
+  for (let row = 0; row < height; row++) {
+    map.push([...''.padStart(width, '.')]);
+  }
+
+  for (let index = rope.length - 1; index >= 0; index--) {
+    const knot = rope[index]!;
+    const posX = knot.x - bounds.minX;
+    const posY = knot.y - bounds.minY;
+    map[posY][posX] = (index % 10).toString();
+  }
+  map.reverse();
+  map.forEach((row) => {
+    console.log(row.join(''));
+  });
+  console.log();
+}
+
+const instructions = input.map((line) => {
+  const [left, right] = line.split(' ') as [string, string];
+  return {
+    direction: left,
+    amount: parseInt(right),
+  } as Instruction;
+});
+
+// Part One
+const visitedPositions: Set<string> = new Set();
+moveRope(instructions, makeRope(), visitedPositions);
+console.log('Solution Part 1:', visitedPositions.size);
+
+visitedPositions.clear();
+moveRope(instructions, makeRope(10), visitedPositions);
+console.log('Solution Part 2:', visitedPositions.size);