A Series of Tubes - Advent of Code - 20171219

ac20171219.js

const path = require('./path');

let changeDirection = function(path, x, y, dX, dY) {
  let newDirections = [[dY, dX], [-1 * dY, -1 * dX]];
  let direction = -1;

  newDirections.forEach((d, i) => {
    let location = path[x + d[0]][y + d[1]];
    if (location !== ' ' && location !== undefined) {
      direction = i;
    }
  });

  return newDirections[direction];
};

let followPath = function(path) {
  let x = 1;
  let y = path[x].indexOf('|');
  let dX = 1;
  let dY = 0;
  let letters = [];
  let steps = 1;

  while (dX || dY) {
    x += dX;
    y += dY;
    let location = path[x][y];

    if (location == ' ') {
      [dX, dY] = [false, false];
      continue;
    }

    if (location.match(/[A-Z]/)) {
      letters.push(location);
    }

    if (location == '+') {
      let direction = changeDirection(path, x, y, dX, dY);
      if (direction) {
        [dX, dY] = direction;
      } else {
        [dX, dY] = [false, false];
      }
    }
    steps++;
  }

  return [letters.join(''), steps];
};

let result;
result = followPath(path);
console.log(result);