https://code.google.com/codejam/contest/1378488/dashboard

gSurvivor.scala

package codejam

import java.io.{File, PrintStream}

import scala.annotation.tailrec
import scala.io.Source


case class Food(expiration: Int, satiety : Int) {
  val sum = expiration + satiety
}

object Survivor {
  def findMaxDate(foods : List[Food]) : Int = {
    val greedyFoods = foods.sortBy(-_.sum)

    def canReach(remain:List[Food], date : Int) : Boolean = {
      if(remain.isEmpty || date < 0 || remain.head.sum < date) return false // remain.head.sum means 'can reach'. it always bigger or equal than date.
      date == 0 ||                                            // find solution
        canReach(remain.tail, date - remain.head.satiety) ||  // eat remain.head
        canReach(remain.tail, date)                           // not eat remain.head
    }

    @tailrec
    def inner(date : Int) : Int = 
      if(canReach(greedyFoods, date)) date else inner(date-1)
    
    inner(greedyFoods.head.sum)
  }

  def process(iter: Iterator[String])(pr: String => Unit) {
    for (count <- 1 to iter.next().toInt) yield {
      val foods = (for(n <- 1 to iter.next().toInt) yield {
        val Array(p, s) = iter.next().split(" ").map(_.toInt)
        Food(p, s)
      }).toList
      pr(s"Case #$count: ${findMaxDate(foods)}")
    }
  }

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