「オフラインリアルタイムどう書く第18回(フォークじゃない)」の問題を解いてみた


[横浜へなちょこプログラミング勉強会](https://yhpg.doorkeeper.jp/)にて過去に出題された[フォークじゃない](http://nabetani.sakura.ne.jp/hena/ord18notfork/)を解いてみた。
回答にかかった時間は20分程度。

ごくごく素直に実装したのだが、`Array#sort`が安定ソートではないため、るりまにある通りの小技を使っている。
そのため`CashierList#choose_cashier`で`first.first`としてしまっており、ここが非常に気持ち悪い。

```ruby
class Cashier
  def initialize capacity
    @capacity = capacity
    @queue = []
  end

  def queue
    @queue.inject(0){|s, n| s + (n === Float::INFINITY ? 1 : n)}
  end

  def add_queue n
    @queue.push n
  end

  def exec
    cap = @capacity
    while cap > 0 and not @queue.empty? do
      @queue[0], cap = [@queue.first - cap, cap - @queue.first]
      @queue.shift if @queue[0] <= 0
    end
  end
end

class CasherList
  def initialize capacities
    @cashiers = capacities.map{|c| Cashier.new c}
  end

  def exec input
    input.chars.each{|c|
      case c
      when (?1..?9), ?x then choose_cachier.add_queue(c === ?x ? Float::INFINITY : c.to_i)
      when ?.           then @cashiers.each{|cashier| cashier.exec}
      end
    }
    @cashiers.map{|cashier| cashier.queue}
  end

  private

  def choose_cachier
    @cashiers.each_with_index.sort_by{|cashier, i| [cashier.queue, i]}.first.first
  end
end

test = <<_TEST
/*0*/ test( "42873x.3.", "0,4,2,0,0" );    
/*1*/ test( "1", "1,0,0,0,0" );    
/*2*/ test( ".", "0,0,0,0,0" );    
/*3*/ test( "x", "1,0,0,0,0" );    
/*4*/ test( "31.", "1,0,0,0,0" );    
/*5*/ test( "3x.", "1,1,0,0,0" );    
/*6*/ test( "99569x", "9,9,6,6,9" );    
/*7*/ test( "99569x33", "9,9,9,9,9" );    
/*8*/ test( "99569x33.", "7,2,6,4,7" );    
/*9*/ test( "99569x33..", "5,0,4,0,5" );    
/*10*/ test( "12345x3333.", "4,0,3,2,3" );    
/*11*/ test( "54321x3333.", "3,0,3,0,4" );    
/*12*/ test( "51423x3333.", "3,4,4,0,4" );    
/*13*/ test( "12x34x.", "1,0,1,0,2" );    
/*14*/ test( "987x654x.32", "7,6,4,10,5" );    
/*15*/ test( "99999999999x99999999.......9.", "20,10,12,5,20" );    
/*16*/ test( "997", "9,9,7,0,0" );    
/*17*/ test( ".3.9", "1,9,0,0,0" );    
/*18*/ test( "832.6", "6,6,0,0,0" );    
/*19*/ test( ".5.568", "3,5,6,8,0" );    
/*20*/ test( "475..48", "4,8,0,0,0" );    
/*21*/ test( "7.2..469", "1,4,6,9,0" );    
/*22*/ test( "574x315.3", "3,3,1,7,1" );    
/*23*/ test( "5.2893.x98", "10,9,5,4,1" );    
/*24*/ test( "279.6xxx..4", "2,1,4,1,1" );    
/*25*/ test( "1.1.39..93.x", "7,1,0,0,0" );    
/*26*/ test( "7677749325927", "16,12,17,18,12" );    
/*27*/ test( "x6235.87.56.9.", "7,2,0,0,0" );    
/*28*/ test( "4.1168.6.197.6.", "0,0,3,0,0" );    
/*29*/ test( "2.8.547.25..19.6", "6,2,0,0,0" );    
/*30*/ test( ".5.3x82x32.1829..", "5,0,5,0,7" );    
/*31*/ test( "x.1816..36.24.429.", "1,0,0,0,7" );    
/*32*/ test( "79.2.6.81x..26x31.1", "1,0,2,1,1" );    
/*33*/ test( "574296x6538984..5974", "14,13,10,15,14" );    
/*34*/ test( "99.6244.4376636..72.6", "5,6,0,0,3" );    
/*35*/ test( "1659.486x5637168278123", "17,16,16,18,17" );    
/*36*/ test( ".5.17797.x626x5x9457.3.", "14,0,3,5,8" );    
/*37*/ test( "..58624.85623..4.7..23.x", "1,1,0,0,0" );    
/*38*/ test( "716.463.9.x.8..4.15.738x4", "7,3,5,8,1" );    
/*39*/ test( "22xx.191.96469472.7232377.", "10,11,18,12,9" );    
/*40*/ test( "24..4...343......4.41.6...2", "2,0,0,0,0" );    
/*41*/ test( "32732.474x153.866..4x29.2573", "7,5,7,8,5" );    
/*42*/ test( "786.1267x9937.17.15448.1x33.4", "4,4,8,4,10" );    
/*43*/ test( "671714849.149.686852.178.895x3", "13,16,13,10,12" );    
/*44*/ test( "86x.47.517..29621.61x937..xx935", "7,11,8,8,10" );    
/*45*/ test( ".2233.78x.94.x59511.5.86x3.x714.", "4,6,10,8,8" );    
/*46*/ test( ".793...218.687x415x13.1...x58576x", "8,11,8,6,9" );    
/*47*/ test( "6.6x37.3x51x932.72x4x33.9363.x7761", "15,13,15,12,15" );    
/*48*/ test( "6..4.x187..681.2x.2.713276.669x.252", "6,7,8,6,5" );    
/*49*/ test( ".6.xx64..5146x897231.x.21265392x9775", "19,17,19,20,17" );    
/*50*/ test( "334.85413.263314.x.6293921x3.6357647x", "14,14,12,16,10" );    
/*51*/ test( "4.1..9..513.266..5999769852.2.38x79.x7", "12,10,13,6,10" );
_TEST

require 'minitest/autorun'

describe 'NotFork' do
  test.split("\n").each do |line|
    t, n, input, expect = line.match(/^\/\*(\d+)\*\/\s*test\(\s*"([^"]+)",\s*"([^"]+)"\s*\);\s*$/).to_a
    list = CasherList.new [2, 7, 3, 5, 2]
    it input do
      assert_equal expect, list.exec(input).join(",")
    end
  end
end
```