robo-santa-houses.coffee

expect = require('chai').expect
_ = require('lodash')



housesDeliveredGrid = (commands) ->
  grid = {0:{0:1}}
  currentX = 0
  currentY = 0

  for command in commands
    switch
      when command is '>'
        currentX += 1
      when command is '^'
        currentY += 1
      when command is '<'
        currentX -= 1
      when command is 'v'
        currentY -= 1

    grid[currentY.toString()] ||= {}
    grid[currentY.toString()][currentX.toString()] = 1

  return grid


gridCount = (grid) ->
  _(grid).values().flatten().values().map(_.values).flatten().sum()

housesDeliveredGridCount = (commands) ->
  gridCount(housesDeliveredGrid(commands))

combineGrids = (grid1, grid2) ->
  for yPos, rows of grid1
    grid2[yPos] ||= {}
    for xPos, v of rows
      grid2[yPos][xPos] = 1
  return grid2

cyborgHousesDelivered = (input) ->
  isOdd = (v, n) -> n %2 is 0
  isEven = (v, n) -> n %2 is 1
  santaCommands = _.filter(input, isOdd)
  roboCommands = _.filter(input, isEven)


  santaGrid = housesDeliveredGrid(santaCommands)
  roboGrid = housesDeliveredGrid(roboCommands)

  compositeGrid = combineGrids(santaGrid, roboGrid)
  gridCount(compositeGrid)

case1 = '>'
case2 = '^>v<'
case3 = '^v^v^v^v^v'

describe 'housesDeliveredGridCount()', ->
  it 'case1 succeeds', ->
    expect(housesDeliveredGridCount(case1)).to.eq(2)
  it 'case2 succeeds', ->
    expect(housesDeliveredGridCount(case2)).to.eq(4)
  it 'case3 succeeds', ->
    expect(housesDeliveredGridCount(case3)).to.eq(2)


case4 = '^v'
case5 = '^>v<'
case6 = '^v^v^v^v^v'
input = require('fs').readFileSync('input.txt').toString()

describe 'cyborgHousesDelivered()', ->
  it 'case4 succeeds', ->
    expect(cyborgHousesDelivered(case4)).to.eq(3)
  it 'case5 succeeds', ->
    expect(cyborgHousesDelivered(case5)).to.eq(3)
  it 'case6 succeeds', ->
    expect(cyborgHousesDelivered(case6)).to.eq(11)
#

console.log 'solution:', cyborgHousesDelivered(input)