BadHorse.scala

package greeter

import scala.collection.mutable
import scala.io.Source
import java.io.{ File, PrintStream }

object hello {

  def isBipartiteGraph(lines: mutable.ListBuffer[(String, String)], map: mutable.HashMap[String, Boolean]): Boolean = {

    var remains = mutable.ListBuffer[(String, String)]()

    lines.map { case (left, right) =>

      if (map.isEmpty) {
        map += (left -> false)
        map += (right -> true)
      }

      (map.contains(left), map.contains(right)) match {
        case (true, true)   => if (map(left) == map(right)) return false
        case (true, false)  => map += right -> !map(left)
        case (false, true)  => map += left -> !map(right)
        case (false, false) => remains = (left, right) +: remains
      }
    }

    if (remains.isEmpty) true
    else {
      if (remains.equals(lines)) isBipartiteGraph(remains, mutable.HashMap.empty)
      else isBipartiteGraph(remains, map)
    }
  }

  def process(iter: Iterator[String])(pr: String => Unit) {

    for (i <- 1 to iter.next().toInt) yield {
      val seq = List.fill(iter.next().toInt){
        val Array(a, b) = iter.next().toString split ' '
        (a, b)
      }
      pr(s"Case #$i: ${if (isBipartiteGraph(mutable.ListBuffer(seq.toSeq: _*), mutable.HashMap.empty)) "Yes" else "No"}")
    }
  }

  def main(args: Array[String]) {
    val in = Source.fromFile(new File("A-small-practice-2.in"))
    val out = new PrintStream(new File("test.out"))
    try {
      process(in.getLines) { s: String => out.println(s) }
    } finally {
      out.flush; out.close
    }
  }
}