DynamicGrid.scala

object DynamicGrid extends App {
  @annotation.tailrec
  def countConnected(ones: Set[(Int, Int)], count: Int = 0): Int = {
    def removeClusterFrom(ones: Set[(Int, Int)], from: (Int, Int)): Set[(Int, Int)] = (for {
      (dr, dc) <- Vector((-1, 0), (0, 1), (1, 0), (0, -1))
      (r, c) = from
      neighbor = (r + dr, c + dc) if ones contains neighbor
    } yield neighbor).foldLeft(ones - from)(removeClusterFrom)

    if (ones.isEmpty) count
    else countConnected(removeClusterFrom(ones, ones.head), count + 1)
  }

  def process(lineIn: Iterator[String])(lineOut: String => Unit) =
    for (i <- 1 to lineIn.next().toInt) {
      val Array(r, c) = lineIn.next().split(' ').map(_.toInt)
      lineOut(s"Case #$i:")
      ((for {
        (line, r) <- Seq.tabulate(r) { (lineIn.next(), _) }.toSet
        (digit, c) <- line.zipWithIndex if digit == '1'
      } yield (r, c)) /: (1 to lineIn.next().toInt)) { (ones, _) =>
        val chars = lineIn.next().split(' ')
        chars.head match {
          case "Q" =>
            lineOut(countConnected(ones).toString)
            ones
          case "M" =>
            val Array(x, y, z) = chars.tail.map(_.toInt)
            Vector(ones - ((x, y)), ones + ((x, y)))(z)
        }
      }
    }

  val filename = "A-large-practice"
  val writer = new java.io.PrintWriter(filename + ".out")
  try {
    process(io.Source.fromFile(filename + ".in").getLines) { s =>
      writer.println(s); writer.flush()
    }
  } finally {
    writer.flush(); writer.close()
  }
}

DynamicGridTest.scala

import org.scalatest._

import DynamicGrid._

class DynamicGridTest extends FunSuite with Matchers {

  test("sample #1-1") {
    assert(countConnected(Set((0,1), (0,3), (1,2), (2,1), (3,0), (3,1), (3,2), (3,3))) === 4)
  }

  test("sample case") {
    val input = """1
4 4
0101
0010
0100
1111
7
Q
M 0 2 1
Q
M 2 2 0
Q
M 2 1 0
Q""".lines

    val expected = """Case #1:
4
2
2
2""".lines

    lineComparison(input, expected)
  }

  test("full small case") {
    val input = io.Source.fromFile("A-small-practice.in").getLines()
    val expected = io.Source.fromFile("A-small-practice.out").getLines()

    lineComparison(input, expected)
  }

  test("full large case") {
    val input = io.Source.fromFile("A-large-practice.in").getLines()
    val expected = io.Source.fromFile("A-large-practice.out").getLines()

    lineComparison(input, expected)
  }

  def lineComparison(input: Iterator[String], expected: Iterator[String]) {
    process(input) { s =>
      for (line <- s.lines) assert(line.trim === expected.next().trim)
    }
    assert(expected.hasNext === false, "Finished too fast.")
  }

}