Class: TakaTicTacToe::ImpossibleAi

Inherits:
Computer
  • Object
show all
Defined in:
lib/taka_tic_tac_toe/ai_difficulty/impossible_ai.rb

Constant Summary collapse

Negative_Infinity = 
-1.0/0

Instance Attribute Summary

Attributes inherited from Computer

#difficulty, #mark, #opponent_mark

Instance Method Summary collapse

Methods inherited from Computer

#initialize, #set_difficulty

Constructor Details

This class inherits a constructor from TakaTicTacToe::Computer

Instance Method Details

#check_game_state(board, mark) ⇒ Object 



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# File 'lib/taka_tic_tac_toe/ai_difficulty/impossible_ai.rb', line 36

def check_game_state(board, mark)
  return 0 if board.is_tie
  return 1 if board.winner == mark
  -1
end

#make_move(board) ⇒ Object 



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# File 'lib/taka_tic_tac_toe/ai_difficulty/impossible_ai.rb', line 6

def make_move(board)
  best_score = Negative_Infinity
  best_index = 0
  board.empty_slots.each do |slots|
    board.set_move(@mark, slots)
    score = -negamax_score(board, -1)
    board.undo_move(slots)
      if score > best_score
        best_score = score
        best_index = slots
      end
  end
  return best_index
end

#negamax_score(board, color) ⇒ Object 



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# File 'lib/taka_tic_tac_toe/ai_difficulty/impossible_ai.rb', line 21

def negamax_score(board, color)
  score = Negative_Infinity

  mark = color == 1 ? @mark : @opponent_mark

  return check_game_state(board, (mark)) if board.has_winner || board.is_tie

  board.empty_slots.each do |slots|
    board.set_move(mark, slots)
    score = [score, -negamax_score(board, -color)].max
    board.undo_move(slots)
  end
  return score
end