http://code.google.com/codejam/contest/dashboard?c=351101#s=p0

Problem A. Store Credit.rb

f = File.open("A-large-practice.in")

num_testcases = f.readline.strip.to_i
casenumber = 1

num_testcases.times do

  credit = f.readline.strip.to_i
  num_items = f.readline.strip.to_i
  prices = f.readline.split(' ').collect {|x| x.to_i}

  #Write positions to a Hash because we want to sort prices and need to remember the position
  positions = {}

  (1..num_items).each do |pos|
    positions[pos] = prices[pos-1]
  end

  #Sort prices in a descending manner.
  sorted_prices = prices.sort.reverse
  
  solved = false
  while !solved

    first_number = sorted_prices[0]
    sorted_prices = sorted_prices[1, num_items-1]

    sorted_prices.each do |second_number|
      if first_number + second_number == credit

        solved = true
        
        indices = []

        first_position = positions.key(first_number)
        indices.push first_position
        positions.delete(first_position)

        second_position = positions.key(second_number)
        indices.push second_position
       
        indices.sort!
        print "Case #" + casenumber.to_s + ": "
        indices.each { |i| print i.to_s +  " "}
        print "\n"
        
        break
      end
    end

  end
  
  casenumber = casenumber + 1

end