day-3-part-1.js

part1 () {
  let rows = _.split(this.input, '\n')
  let grid = _.times(MAX_DIM * MAX_DIM, _.constant(0))

  _.each(rows, v => {
    let [x, y, w, h] = _
      .chain(v.match(/#\d+ @ (\d+),(\d+): (\d+)x(\d+)/)) // separate parts
      .tail() // discard full match
      .map(Number) // cast to numbers
      .value() // destructure to variables

    let origin = x + y * MAX_DIM // top left corner of claim

    _.each(_.range(h), hh => {
      _.each(_.range(w), ww => {
        let point = origin + ww + hh * MAX_DIM // unique point "index" in grid

        grid[point]++ // tally the claim
      })
    })
  })

  let claims = _.countBy(grid, v => v > 1 ? 'over' : 'good')

  this.solution1 = claims.over
}