Elixir实现War卡牌游戏遇测试失败，求排查方案

游戏规则 #

• 洗牌后的52张牌（1-13各4张）交替发给两名玩家，每人26张。
• 每轮双方亮出顶牌：等级高的玩家将本轮所有牌按降序放入自己牌堆底部。
• 若顶牌平局则触发战争：每人放1张暗牌+1张明牌，明牌等级高的玩家赢得所有牌；若仍平局则重复此过程，直到分出胜负。
• 任一玩家牌耗尽则失败，另一方获胜。

技术要求 #

输入为1-13各4个的52整数排列，程序需模拟游戏至一方牌耗尽，返回获胜玩家的完整牌堆（按规则排序）。

测试用例 #

defmodule WarTest do
  use ExUnit.Case

  describe "War" do
    test "deal_1" do
      t1 = [1,1,1,1,13,13,13,13,11,11,11,11,12,12,12,12,10,10,10,10,9,9,9,9,7,7,7,7,8,8,8,8,6,6,6,6,5,5,5,5,4,4,4,4,3,3,3,3,2,2,2,2]
      r1 = [1,1,1,1,13,13,13,13,12,12,12,12,11,11,11,11,10,10,10,10,9,9,9,9,8,8,8,8,7,7,7,7,6,6,6,6,5,5,5,5,4,4,4,4,3,3,3,3,2,2,2,2]
      assert War.deal(t1) == r1
    end

    test "deal_2" do
      t2 = [1,13,1,13,1,13,1,13,12,11,12,11,12,11,12,11,10,9,10,9,10,9,10,9,8,7,8,7,8,7,8,7,6,5,6,5,6,5,6,5,4,3,4,3,4,3,4,3,2,2,2,2]
      r2 = [4,3,2,2,2,2,4,3,4,3,4,3,6,5,6,5,6,5,6,5,8,7,8,7,8,7,8,7,10,9,10,9,10,9,10,9,12,11,12,11,12,11,12,11,1,13,1,13,1,13,1,13]
      assert War.deal(t2) == r2
    end

    test "deal_3" do
      t3 = [13,1,13,1,13,1,13,1,11,12,11,12,11,12,11,12,9,10,9,10,9,10,9,10,7,8,7,8,7,8,7,8,5,6,5,6,5,6,5,6,3,4,3,4,3,4,3,4,2,2,2,2]
      r3 = [4,3,2,2,2,2,4,3,4,3,4,3,6,5,6,5,6,5,6,5,8,7,8,7,8,7,8,7,10,9,10,9,10,9,10,9,12,11,12,11,12,11,12,11,1,13,1,13,1,13,1,13]
      assert War.deal(t3) == r3
    end

    test "deal_4" do
      t4 = [10,11,12,13,1,2,3,4,5,6,7,8,9,10,11,12,13,1,2,3,4,5,6,7,8,9,10,11,12,13,1,2,3,4,5,6,7,8,9,10,11,12,13,1,2,3,4,5,6,7,8,9]
      r4 = [1,1,13,12,9,5,11,4,9,3,8,7,7,2,13,10,12,5,10,4,9,6,8,3,1,1,13,12,7,5,11,4,9,3,8,6,7,2,13,10,12,5,11,11,10,8,6,4,6,3,2,2]
      assert War.deal(t4) == r4
    end

    test "deal_5" do
      t5 = [1,2,3,4,5,6,7,8,9,10,11,12,13,1,2,3,4,5,6,7,8,9,10,11,12,13,1,2,3,4,5,6,7,8,9,10,11,12,13,1,2,3,4,5,6,7,8,9,10,11,12,13]
      r5 = [1,10,13,8,11,9,8,7,11,8,13,7,13,6,12,6,9,5,8,5,7,4,7,4,11,6,12,10,6,3,2,2,12,5,9,3,10,4,9,2,10,3,5,2,1,1,1,13,12,11,4,3]
      assert War.deal(t5) == r5
    end
  end
end

核心实现代码 #

defmodule War do
  defp play_game(p1, p2, tied \ [])

  defp play_game([], p2, tied), do: p2 ++ tied
  defp play_game(p1, [], tied), do: p1 ++ tied

  # War, cards tied
  defp play_game([c | xs], [c | ys], tied) do
    cards = Enum.sort([c, c] ++ tied, :desc)
    play_game(xs, ys, cards)
  end

  # Normal game turn
  defp play_game([x | xs], [y | ys], tied) do
    cards = Enum.sort([x, y] ++ tied, :desc)

    if x > y do
      play_game(xs ++ cards, ys)
    else
      play_game(xs, ys ++ cards)
    end
  end
end

当前问题 #

当前实现仅通过第一个测试用例，其余测试均失败，需要排查问题并给出解决方法。

内容的提问来源于stack exchange，提问作者Zoey