CrazyRows.scala

object CrazyRows extends App {

  def minSwap(matrix: IndexedSeq[String]): Int =
    ((matrix map (_ lastIndexOf '1'), 0) /: (0 until matrix.size)) {
      case ((rows, acc), limit) =>
        val target = rows indexWhere { _ <= limit }
        val (front, end) = rows splitAt target
        (front ++ end.tail, acc + target)
    }._2

  def process(lineIn: Iterator[String])(lineOut: String => Unit) =
    for (i <- 1 to lineIn.next().toInt) {
      val n = lineIn.next().toInt
      val matrix = IndexedSeq.fill(n) { lineIn.next() }
      lineOut(s"Case #$i: ${minSwap(matrix)}")
    }

  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()
  }

}

CrazyRowsTest.scala

import org.scalatest._

import CrazyRows._

class CrazyRowsTest extends FunSuite {
  
  test("sample #1") {
    val matrix = Vector("10", "11")
    assert(minSwap(matrix) === 0)
  }
  
  test("sample #2") {
    val matrix = Vector("001", "100", "010")
    assert(minSwap(matrix) === 2)
  }
  
  test("sample #3") {
    val matrix = Vector("1110", "1100", "1100", "1000")
    assert(minSwap(matrix) === 4)
  }
  
  test("sample case") {
    val input = """3
2
10
11
3
001
100
010
4
1110
1100
1100
1000""".lines

    val expected = """Case #1: 0
Case #2: 2
Case #3: 4""".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.ref").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.ref").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.")
  }

}