Sporifica Virus - Advent of Code - 20171222

ac20171222.js

let virusGrid = require('./virusGrid');

let checkGridSize = function(grid, x, y) {
  let width = grid[0].length;

  if (x < 0) {
    grid.unshift(new Array(width).fill(0).map(v => '.'));
    x = 0;
  }
  if (x == grid.length) {
    grid.push(new Array(width).fill(0).map(v => '.'));
  }
  if (y < 0) {
    grid.forEach(v => {
      v.unshift('.');
    });
    y = 0;
  }
  if (y == grid[0].length) {
    grid.forEach(v => {
      v.push('.');
    });
  }

  return [grid, x, y];
};

let virusWorker_1 = function(grid, iterations) {
  let x = (y = Math.floor(grid.length / 2));
  let directions = [
    [-1, 0], // north
    [0, 1], // east
    [1, 0], // south
    [0, -1] // west
  ];
  let getNewDirection = function(direction, change) {
    return (directions.length + direction + change) % directions.length;
  };

  let currentDirection = 0;
  let left = -1;
  let right = 1;

  let infections = 0;

  for (let i = 0; i < iterations; i++) {
    //console.log('x, y, direction', x, y, currentDirection);
    let state = grid[x][y];
    if (state == '.') {
      grid[x][y] = '#';
      infections++;
      currentDirection = getNewDirection(currentDirection, left);
      x += directions[currentDirection][0];
      y += directions[currentDirection][1];
    } else {
      grid[x][y] = '.';
      currentDirection = getNewDirection(currentDirection, right);
      x += directions[currentDirection][0];
      y += directions[currentDirection][1];
    }
    [grid, x, y] = checkGridSize(grid, x, y);
    //console.log(grid.map(v => v.join('')).join('\n'));
  }

  return infections;
};

let virusWorker_2 = function(grid, iterations) {
  let x = (y = Math.floor(grid.length / 2));
  let directions = [
    [-1, 0], // north
    [0, 1], // east
    [1, 0], // south
    [0, -1] // west
  ];
  let getNewDirection = function(direction, change) {
    return (directions.length + direction + change) % directions.length;
  };

  let currentDirection = 0;
  let left = -1;
  let right = 1;
  let reverse = 2;

  let infections = 0;

  for (let i = 0; i < iterations; i++) {
    //console.log('x, y, direction', x, y, currentDirection);
    let state = grid[x][y];
    switch (state) {
      case '.':
        grid[x][y] = 'W';
        currentDirection = getNewDirection(currentDirection, left);
        x += directions[currentDirection][0];
        y += directions[currentDirection][1];
        break;
      case 'W':
        grid[x][y] = '#';
        infections++;
        x += directions[currentDirection][0];
        y += directions[currentDirection][1];
        break;
      case '#':
        grid[x][y] = 'F';
        currentDirection = getNewDirection(currentDirection, right);
        x += directions[currentDirection][0];
        y += directions[currentDirection][1];
        break;
      case 'F':
        grid[x][y] = '.';
        currentDirection = getNewDirection(currentDirection, reverse);
        x += directions[currentDirection][0];
        y += directions[currentDirection][1];
        break;
    }

    [grid, x, y] = checkGridSize(grid, x, y);
    //console.log(grid.map(v => v.join('')).join('\n'));
  }

  return infections;
};

let virusWorker = virusWorker_2;
let iterations = 10000000;
let result = virusWorker(virusGrid, iterations);
console.log(result);