Advent of Code 2022 - Day 9: Rope Bridge Solution

Part 1

Use Set to store unique coordinations visited by tail

Implementation

1const fs = require("fs")
2
3const readData = () => {
4  const data = fs
5    .readFileSync("./input", "utf-8")
6    .split(/\r?\n/)
7    .map(row => row.split(" "))
8
9  return data
10}
11
12const main = () => {
13  const data = readData()
14  const coordSet = new Set()
15  const ROPE_LENGTH = 2
16  const rope = Array.from({ length: ROPE_LENGTH }, _ => ({ x: 0, y: 0 }))
17
18  const dirDelta = {
19    U: { x: 0, y: -1 },
20    D: { x: 0, y: 1 },
21    L: { x: -1, y: 0 },
22    R: { x: 1, y: 0 },
23  }
24
25  for (const [dir, numberOfSteps] of data) {
26    let stepsLeft = +numberOfSteps
27    const [head, tail] = [rope[0], rope.slice(-1)[0]]
28
29    while (stepsLeft--) {
30      head.x += dirDelta[dir].x
31      head.y += dirDelta[dir].y
32
33      for (let i = 1; i < rope.length; i++) {
34        const [prev, curr] = [rope[i - 1], rope[i]]
35        const delta = {
36          x: prev.x - curr.x,
37          y: prev.y - curr.y,
38        }
39
40        if (Math.abs(delta.x) >= 2 || Math.abs(delta.y) >= 2) {
41          delta.x = delta.x === 0 ? 0 : delta.x > 0 ? 1 : -1
42          delta.y = delta.y === 0 ? 0 : delta.y > 0 ? 1 : -1
43
44          curr.x += delta.x
45          curr.y += delta.y
46        }
47      }
48
49      coordSet.add(`${tail.x} ${tail.y}`)
50    }
51  }
52
53  const res = coordSet.size
54
55  console.log(res)
56}
57
58main()

Part 2

Change ROPE_LENGTH to 10

Implementation

1// ...
2const ROPE_LENGTH = 10
3// ...

References

Original problem