def check_corners(game: ReversiGame) -> tuple[int, int]:
"""Return a tuple representing the number of corner taken by each side
:param game: the game state to be checked
:return: (corner taken by black, corner taken by white)
"""
board = game.get_game_board()
corner_black, corner_white = 0, 0
for i in [0, game.get_size() - 1]:
for j in [0, game.get_size() - 1]:
if board[i][j] == BLACK:
corner_black += 1
elif board[i][j] == WHITE:
corner_white += 1
return corner_black, corner_white
def _value_eval(self, game: ReversiGame, piece: str) -> Union[float, int]:
"""The evaluation function for minimax. For Positional Player, the evaluation function
will evaluate the positional advantage of the pieces on the board.
Preconditions:
- piece in {BLACK, WHITE}
:param game: the current game state for evaluation
:return: value evaluated from the current game state
"""
if game.get_winner() is not None:
if game.get_winner() == piece: # win
return math.inf
elif game.get_winner() == 'Draw': # draw
return 0
else: # lose
return -math.inf
else:
num_black, num_white = game.get_num_pieces(
)[BLACK], game.get_num_pieces()[WHITE]
corner_black, corner_white = check_corners(game)
board_filled = (num_black + num_white) / (game.get_size()**2)
if piece == BLACK:
if board_filled < 0.80: # early to middle game
return 10 * (corner_black - corner_white) + len(
game.get_valid_moves())
else: # end game
return num_black / num_white
else:
if board_filled < 0.80: # early to middle game
return 10 * (corner_white - corner_black) + len(
game.get_valid_moves())
else: # end game
return num_white / num_black
def positional_early(game: ReversiGame, selected_board_weight: list,
player: str) -> Union[float, int]:
"""Evaluates a board based on the positional advantage of black
Preconditions:
player in {BLACK, WHITE}
"""
if player == BLACK:
opponent = WHITE
else:
opponent = BLACK
eval_so_far = 0
board = game.get_game_board()
for i in range(game.get_size() - 1):
for j in range(game.get_size() - 1):
if board[i][j] == player:
eval_so_far += selected_board_weight[i][j]
elif board[i][j] == opponent:
eval_so_far -= selected_board_weight[i][j]
return eval_so_far
def _value_eval(self, game: ReversiGame, piece: str) -> Union[float, int]:
"""The evaluation function for minimax. For Positional Player, the evaluation function
will evaluate the positional advantage of the pieces on the board.
Preconditions:
- piece in {BLACK, WHITE}
:param game: the current game state for evaluation
:return: value evaluated from the current game state
"""
if game.get_winner() is not None:
if game.get_winner() == piece: # win
return math.inf
elif game.get_winner() == 'Draw': # draw
return 0
else: # lose
return -math.inf
else:
num_black, num_white = game.get_num_pieces(
)[BLACK], game.get_num_pieces()[WHITE]
board_filled = (num_black + num_white) / (game.get_size()**2)
if game.get_size() == 8:
selected_board_weight = BOARD_WEIGHT_8
else:
selected_board_weight = BOARD_WEIGHT_6
if board_filled < 0.80:
return positional_early(game, selected_board_weight, piece)
else:
if piece == BLACK:
return num_black / num_white
if piece == WHITE:
return num_white / num_black
return 0
