CommonRectsArea.scala

CommonRectsArea.scala

// find a common area of two (probably intersected) rectangles

object CommonRectsArea extends App {

  type Coord = (Int, Int)

  class Rect(val bottomLeft: Coord, val topRight: Coord) {
    def width: Int = topRight._1 - bottomLeft._1
    def height: Int = topRight._2 - bottomLeft._2
    def area: Int = width * height
  }

  private def intersectionArea(a: Rect, b: Rect): Int = {
    val w = (a.bottomLeft._1 until a.topRight._1) intersect (b.bottomLeft._1 until b.topRight._1)
    val h = (a.bottomLeft._2 until a.topRight._2) intersect (b.bottomLeft._2 until b.topRight._2)
    w.size * h.size
  }

  def commonArea(bottomLeftA: Coord, topRightA: Coord, bottomLeftB: Coord, topRightB: Coord): Int =
    commonArea(
      new Rect(bottomLeftA, topRightA),
      new Rect(bottomLeftB, topRightB)
    )

  def commonArea(a: Rect, b: Rect): Int =
    a.area + b.area - intersectionArea(a, b)

  assert(
    commonArea(
      (0, 0), (3, 2), (2, 1), (4, 3)
    ) == 9
  )

}