Problems calling a recursive function on a multi-dimensional nested array

Question

I am trying to split the sub-arrays if there are more than 8. I have tried calling the rps_tournament_winner function on players if it has a flattened length longer than 16 but I get a "stack too deep error".

Do I have to work on the players variable or tournament? I'm looking for a nudge in the right direction; not a complete solution.

def rps_tournament_winner(tournament)
  return rps_game_winner(tournament) if tournament.flatten.length == 4
  players = tournament.flatten(2)  

  while players.length > 1
    players = players.each_slice(2).map { |x| rps_game_winner(x) }
  end

  players[0]
end

Looks like you're recursively calling the function without modifying the argument before doing so. This would cause an infinite loop. You need to reduce the argument tournament in some way first. — Madbreaks
– Madbreaks, Commented Mar 1, 2012 at 20:21
So if I check for length and if it is over a certain length could I split it into 2 smaller arrays and call the tournament function on each? — The_Cthulhu_Kid
– The_Cthulhu_Kid, Commented Mar 1, 2012 at 20:27
Got it sorted, thanks. Was able to tweak an If statement and got it running perfectly. Thanks for the help! — The_Cthulhu_Kid
– The_Cthulhu_Kid, Commented Mar 3, 2012 at 7:38
You should be able to delete your question yourself, if that's what you want to do. — Carl Norum
– Carl Norum, Commented Mar 3, 2012 at 7:49
You can add your own answer and accept that. It may help someone in the future and you don't lose reputation. — Mischa
– Mischa, Commented Mar 3, 2012 at 8:58

PeterParameter · Accepted Answer · 2012-03-06 19:23:03Z

6

This is the shortest I was able to come up with (with recursion)

def rps_tournament_winner(games)
   if games.flatten.length > 4
     rps_game_winner([rps_tournament_winner(games[0]), rps_tournament_winner(games[1])])
   else
     rps_game_winner(games)
   end
end

answered Mar 6, 2012 at 19:23

PeterParameter

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2 Comments

The_Cthulhu_Kid Over a year ago

I think recursion was the way to go, nice solution =D

PeterParameter Over a year ago

Yeah, when I realized flatten could be used, it became kind of obvious and it hit me :). Thanks :)

Jaitls · Accepted Answer · 2012-08-06 23:17:35Z

5

This is also an elegant solution w/o flattening the array:

def rps_tournament_winner(tournament)
    if tournament[0][0].is_a?(Array)
        tournament =[rps_tournament_winner(tournament[0]), rps_tournament_winner(tournament[1])]
    end
    rps_game_winner(tournament)
end

answered Aug 6, 2012 at 23:17

Jaitls

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Comments

Rustam · Accepted Answer · 2012-03-04 14:53:25Z

1

I solved it using recursion

class WrongNumberOfPlayersError < StandardError ; end
class NoSuchStrategyError < StandardError ; end

def rps_game_winner(game)
  raise WrongNumberOfPlayersError unless game.length == 2
  if game[0][0].is_a?(Array) then
    winner1 = rps_game_winner(game[0])
    winner2 = rps_game_winner(game[1])
    game = [winner1, winner2]
  end
  raise NoSuchStrategyError unless /^(P|R|S){2}$/ =~ game[0][1] + game[1][1]
  case game[0][1]
    when "R"
      if game[1][1] == "P" then
        game[1]
      else
        game[0]
      end
    when "P"
      if game[1][1] == "S" then
        game[1]
      else 
        game[0]
      end
    when "S"
      if game[1][1] == "R" then
        game[1]
      else
        game[0]
      end
  end
end

def rps_tournament_winner(tournament)
  rps_game_winner(tournament)
end

edited Mar 4, 2012 at 14:53

answered Mar 4, 2012 at 14:43

Rustam

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1 Comment

The_Cthulhu_Kid Over a year ago

Cool =) I love how there are always multiple ways to solve programming problems (I am fairly new to programming at all)

The_Cthulhu_Kid · Accepted Answer · 2012-03-03 19:08:11Z

Only answering this to close the question, hopefully my answer will help some one else =D

After staring at it for about three hours, my mind actually stopped napping and i came up with this:

def rps_tournament_winner(tournament)
  return rps_game_winner(tournament) if tournament.flatten.length == 4
  if tournament.flatten.length == 16
    players = tournament.flatten(2)
  else
    players = tournament.flatten(4)  
  end

  while players.length > 1
    players = players.each_slice(2).map { |x| rps_game_winner(x) }
  end

players[0]
end

The if statement allows me to check that if a tournament of 8 or more players (the testing was only for 8, 16 and 32 players so I doubt this would work for larger sets) My problem before was that I would only flatten(2) which for the larger tournament would not work.

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