Advent-of-Code-2022/22/solution.mjs

import { readFileSync } from 'node:fs';

const input = readFileSync('input', 'utf-8');

const [mapData, pathData] = input.split('\n\n');

const F = {
  R: 0,
  D: 1,
  L: 2,
  U: 3,
  invert: (facing) => {
    switch (facing) {
      case F.R: return F.L;
      case F.D: return F.U;
      case F.L: return F.R;
      case F.U: return F.D;
    }
  },
  rotateR: (facing) => {
    switch (facing) {
      case F.R: return F.D;
      case F.D: return F.L;
      case F.L: return F.U;
      case F.U: return F.R;
    }
  },
  rotateL: (facing) => {
    switch (facing) {
      case F.R: return F.U;
      case F.U: return F.L;
      case F.L: return F.D;
      case F.D: return F.R;
    }
  }
};

class Map {
  constructor(mapData) {
    this.data = mapData
      .split('\n')
      .filter(line => !!line.trim());

    this.height = this.data.length;
    this.width = this.data.reduce((max, row) => Math.max(max, row.length), 0);

    this.portals = {};
  }

  get startingPosition() {
    const pos = [1, 1];

    while (this.get(...pos) !== '.') {
      pos[0]++;
    }

    return pos;
  }

  cubeMode() {
    if (this.width !== 150 || this.height !== 200) {
      throw new Error('Cube mode only works with full size map');
    }
    this.portals = {};

    const e1 = this._edge([51, 1], [100, 1]);
    const e2 = this._edge([101, 1], [150, 1]);
    const e3 = this._edge([51, 1], [51, 50]);
    const e4 = this._edge([150, 1], [150, 50]);
    const e5 = this._edge([101, 50], [150, 50]);
    const e6 = this._edge([51, 51], [51, 100]);
    const e7 = this._edge([100, 51], [100, 100]);
    const e8 = this._edge([1, 101], [50, 101]);
    const e9 = this._edge([1, 101], [1, 150]);
    const e10 = this._edge([100, 101], [100, 150]);
    const e11 = this._edge([51, 150], [100, 150]);
    const e12 = this._edge([1, 151], [1, 200]);
    const e13 = this._edge([50, 151], [50, 200]);
    const e14 = this._edge([1, 200], [50, 200]);

    this._portalEdge(e1, F.U, e12, F.R);
    this._portalEdge(e2, F.U, e14, F.U);
    this._portalEdge([...e3].reverse(), F.L, e9, F.R);
    this._portalEdge([...e4].reverse(), F.R, e10, F.L);
    this._portalEdge(e5, F.D, e7, F.L);
    this._portalEdge(e6, F.L, e8, F.D);
    this._portalEdge(e11, F.D, e13, F.L);
  }

  flatMode() {
    this.portals = {};
    for (let row = 1; row <= this.height; row++) {
      let col = 1;
      while (this.get(col, row) === ' ') col++;
      const start = [col, row];
      while (this.get(col + 1, row) !== ' ') col++;
      const end = [col, row];

      this.portals[[start, F.L]] = [end, F.L];
      this.portals[[end, F.R]] = [start, F.R];
    }

    for (let col = 1; col <= this.width; col++) {
      let row = 1;
      while (this.get(col, row) === ' ') row++;
      const start = [col, row];
      while (this.get(col, row + 1) !== ' ') row++;
      const end = [col, row];

      this.portals[[start, F.U]] = [end, F.U];
      this.portals[[end, F.D]] = [start, F.D];
    }
  }

  get(col, row) {
    const x = col - 1;
    const y = row - 1;

    if (y < 0 || y >= this.data.length || x < 0 || x >= this.data[y].length) {
      return ' ';
    }

    return this.data[y][x];
  }

  nextPos(pos, facing) {
    if (this.portals[[pos, facing]]) return this.portals[[pos, facing]];
    return [[
      pos[0] + (facing === F.R ? 1 : (facing === F.L ? -1 : 0)),
      pos[1] + (facing === F.D ? 1 : (facing === F.U ? -1 : 0)),
    ], facing];
  }

  _portalEdge(fromEdge, fromFacing, toEdge, toFacing) {
    if (fromEdge.length !== toEdge.length) {
      throw new Error('fromEdge must be the same length as toEdge');
    }

    for (let i = 0; i < fromEdge.length; i++) {
      const fromPos = fromEdge[i];
      const toPos = toEdge[i];

      this.portals[[fromPos, fromFacing]] = [toPos, toFacing];
      this.portals[[toPos, F.invert(toFacing)]] =
        [fromPos, F.invert(fromFacing)];
    }
  }

  _edge(start, end) {
    if (start[0] !== end[0] && start[1] !== end[1]) {
      throw new Error("Edges can't be diagonal");
    }

    const colDiff = end[0] - start[0];
    const colIncr = colDiff / (Math.abs(colDiff) || 1);

    const rowDiff = end[1] - start[1];
    const rowIncr = rowDiff / (Math.abs(rowDiff) || 1);

    const edge = [];

    let col = start[0];
    let row = start[1];

    edge.push([col, row]);
    do {
      col += colIncr;
      do {
        row += rowIncr;
        edge.push([col, row]);
      } while (row !== end[1])
    } while (col !== end[0])

    return edge;
  }
}

class Walker {
  constructor(map) {
    this.map = map;
    this.facing = F.R;
    this.pos = this.map.startingPosition;
  }
  
  walk(paces) {
    for (let p = 0; p < paces; p++) {
      const [nextPos, nextFacing] = this.map.nextPos(this.pos, this.facing);
      let nextTile = this.map.get(...nextPos);

      if (nextTile === ' ') {
        throw new Error('Escaped Map!');
      }

      if (nextTile === '#') {
        break;
      }

      this.pos = nextPos;
      this.facing = nextFacing;
    }
  }

  get password() {
    return (
      this.pos[1] * 1000 +
      this.pos[0] * 4 +
      this.facing
    );
  }

  rotateCounterclockwise() {
    this.facing = F.rotateL(this.facing);
  }

  rotateClockwise() {
    this.facing = F.rotateR(this.facing);
  }
}

const instructions = pathData
  .split('\n')
  .filter(line => !!line.trim())
  .join('')
  .split(/(L|R)/)
  .filter(instruction => !!instruction.trim())
  .map(instruction => {
    const num = parseInt(instruction);
    return isNaN(num) ? instruction : num
  });

function runInstructions(walker) {
  for (const instruction of instructions) {
    if (typeof instruction === 'number') {
      walker.walk(instruction);
    } else if (instruction === 'L') {
      walker.rotateCounterclockwise();
    } else if (instruction === 'R') {
      walker.rotateClockwise();
    } else {
      throw new Error(`Invalid instruction: ${instruction}`);
    }
  }
}


const map = new Map(mapData);

map.flatMode();
const flatWalker = new Walker(map);
runInstructions(flatWalker);
console.log('The password for the flat map is:', flatWalker.password);

map.cubeMode();
const cubeWalker = new Walker(map)
runInstructions(cubeWalker);
console.log('The password for the cube map is:', cubeWalker.password);