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import copy
from typing import List, Dict, Any, Tuple, Union
import numpy as np
class Connect4RuleBot():
"""
Overview:
The rule-based bot for the Connect4 game. The bot follows a set of rules in a certain order until a valid move is found.\
The rules are: winning move, blocking move, do not take a move which may lead to opponent win in 3 steps, \
forming a sequence of 3, forming a sequence of 2, and a random move.
"""
def __init__(self, env: Any, player: int) -> None:
"""
Overview:
Initializes the bot with the game environment and the player it represents.
Arguments:
- env: The game environment, which contains the game state and allows interactions with it.
- player: The player that the bot represents in the game.
"""
self.env = env
self.current_player = player
self.players = self.env.players
def get_rule_bot_action(self, board: np.ndarray, player: int) -> int:
"""
Overview:
Determines the next action of the bot based on the current game board and player.
Arguments:
- board(:obj:`array`): The current game board.
- player(:obj:`int`): The current player.
Returns:
- action(:obj:`int`): The next action of the bot.
"""
self.legal_actions = self.env.legal_actions
self.current_player = player
self.next_player = self.players[0] if self.current_player == self.players[1] else self.players[1]
self.board = np.array(copy.deepcopy(board)).reshape(6, 7)
# Check if there is a winning move.
for action in self.legal_actions:
if self.is_winning_move(action):
return action
# Check if there is a move to block opponent's winning move.
for action in self.legal_actions:
if self.is_blocking_move(action):
return action
# Remove the actions which may lead to opponent to win.
self.remove_actions()
# If all the actions are removed, then randomly select an action.
if len(self.legal_actions) == 0:
return np.random.choice(self.env.legal_actions)
# Check if there is a move to form a sequence of 3.
for action in self.legal_actions:
if self.is_sequence_3_move(action):
return action
# Check if there is a move to form a sequence of 2.
for action in self.legal_actions:
if self.is_sequence_2_move(action):
return action
# Randomly select a legal move.
return np.random.choice(self.legal_actions)
def is_winning_move(self, action: int) -> bool:
"""
Overview:
Checks if an action is a winning move.
Arguments:
- action(:obj:`int`): The action to be checked.
Returns:
- result(:obj:`bool`): True if the action is a winning move; False otherwise.
"""
piece = self.current_player
row = self.get_available_row(action)
if row is None:
return False
temp_board = self.board.copy()
temp_board[row][action] = piece
return self.check_four_in_a_row(temp_board, piece)
def is_winning_move_in_two_steps(self, action: int) -> bool:
"""
Overview:
Checks if an action can lead to win in 2 steps.
Arguments:
- action(:obj:`int`): The action to be checked.
Returns:
- result(:obj:`bool`): True if the action is a winning move; False otherwise.
"""
piece = self.current_player
row = self.get_available_row(action)
if row is None:
return False
temp_board = self.board.copy()
temp_board[row][action] = piece
blocking_count = 0
temp = [self.board.copy(), self.current_player]
self.board = temp_board
self.current_player = 3 - self.current_player
legal_actions = [i for i in range(7) if self.board[0][i] == 0]
for action in legal_actions:
if self.is_winning_move(action):
self.board, self.current_player = temp
return False
if self.is_blocking_move(action):
blocking_count += 1
self.board, self.current_player = temp
if blocking_count >= 2:
return True
else:
return False
def is_blocking_move(self, action: int) -> bool:
"""
Overview:
Checks if an action can block the opponent's winning move.
Arguments:
- action(:obj:`int`): The action to be checked.
Returns:
- result(:obj:`bool`): True if the action can block the opponent's winning move; False otherwise.
"""
piece = 2 if self.current_player == 1 else 1
row = self.get_available_row(action)
if row is None:
return False
temp_board = self.board.copy()
temp_board[row][action] = piece
return self.check_four_in_a_row(temp_board, piece)
def remove_actions(self) -> None:
"""
Overview:
Remove the actions that may cause the opponent win from ``self.legal_actions``.
"""
temp_list = self.legal_actions.copy()
for action in temp_list:
temp = [self.board.copy(), self.current_player]
piece = self.current_player
row = self.get_available_row(action)
if row is None:
break
self.board[row][action] = piece
self.current_player = self.next_player
legal_actions = [i for i in range(7) if self.board[0][i] == 0]
# print(f'if we take action {action}, then the legal actions for opponent are {legal_actions}')
for a in legal_actions:
if self.is_winning_move(a) or self.is_winning_move_in_two_steps(a):
self.legal_actions.remove(action)
# print(f"if take action {action}, then opponent take{a} may win")
# print(f"so we should take action from {self.legal_actions}")
break
self.board, self.current_player = temp
def is_sequence_3_move(self, action: int) -> bool:
"""
Overview:
Checks if an action can form a sequence of 3 pieces of the bot.
Arguments:
- action(:obj:`int`): The action to be checked.
Returns:
- result(:obj:`bool`): True if the action can form a sequence of 3 pieces of the bot; False otherwise.
"""
piece = self.current_player
row = self.get_available_row(action)
if row is None:
return False
temp_board = self.board.copy()
temp_board[row][action] = piece
return self.check_sequence_in_neighbor_board(temp_board, piece, 3, action)
def is_sequence_2_move(self, action: int) -> bool:
"""
Overview:
Checks if an action can form a sequence of 2 pieces of the bot.
Arguments:
- action(:obj:`int`): The action to be checked.
Returns:
- result(:obj:`bool`): True if the action can form a sequence of 2 pieces of the bot; False otherwise.
"""
piece = self.current_player
row = self.get_available_row(action)
if row is None:
return False
temp_board = self.board.copy()
temp_board[row][action] = piece
return self.check_sequence_in_neighbor_board(temp_board, piece, 2, action)
def get_available_row(self, col: int) -> bool:
"""
Overview:
Gets the available row for a given column.
Arguments:
- col(:obj:`int`): The column to be checked.
Returns:
- row(:obj:`int`): The available row in the given column; None if the column is full.
"""
for row in range(5, -1, -1):
if self.board[row][col] == 0:
return row
return None
def check_sequence_in_neighbor_board(self, board: np.ndarray, piece: int, seq_len: int, action: int) -> bool:
"""
Overview:
Checks if a sequence of the bot's pieces of a given length can be formed in the neighborhood of a given action.
Arguments:
- board(:obj:`int`): The current game board.
- piece(:obj:`int`): The piece of the bot.
- seq_len(:obj:`int`) The length of the sequence.
- action(:obj:`int`): The action to be checked.
Returns:
- result(:obj:`bool`): True if such a sequence can be formed; False otherwise.
"""
# Determine the row index where the piece fell
row = self.get_available_row(action)
# Check horizontal locations
for c in range(max(0, action - seq_len + 1), min(7 - seq_len + 1, action + 1)):
window = list(board[row, c:c + seq_len])
if window.count(piece) == seq_len:
return True
# Check vertical locations
for r in range(max(0, row - seq_len + 1), min(6 - seq_len + 1, row + 1)):
window = list(board[r:r + seq_len, action])
if window.count(piece) == seq_len:
return True
# Check positively sloped diagonals
for r in range(6):
for c in range(7):
if r - c == row - action:
window = [board[r - i][c - i] for i in range(seq_len) if 0 <= r - i < 6 and 0 <= c - i < 7]
if len(window) == seq_len and window.count(piece) == seq_len:
return True
# Check negatively sloped diagonals
for r in range(6):
for c in range(7):
if r + c == row + action:
window = [board[r - i][c + i] for i in range(seq_len) if 0 <= r - i < 6 and 0 <= c + i < 7]
if len(window) == seq_len and window.count(piece) == seq_len:
return True
return False
def check_four_in_a_row(self, board: np.ndarray, piece: int) -> bool:
"""
Overview:
Checks if there are four of the bot's pieces in a row on the current game board.
Arguments:
- board(:obj:`int`): The current game board.
- piece(:obj:`int`): The piece of the bot.
Returns:
- Result(:obj:`bool`): True if there are four of the bot's pieces in a row; False otherwise.
"""
# Check horizontal locations
for col in range(4):
for row in range(6):
if board[row][col] == piece and board[row][col + 1] == piece and board[row][col + 2] == piece and \
board[row][col + 3] == piece:
return True
# Check vertical locations
for col in range(7):
for row in range(3):
if board[row][col] == piece and board[row + 1][col] == piece and board[row + 2][col] == piece and \
board[row + 3][col] == piece:
return True
# Check positively sloped diagonals
for row in range(3):
for col in range(4):
if board[row][col] == piece and board[row + 1][col + 1] == piece and board[row + 2][
col + 2] == piece and board[row + 3][col + 3] == piece:
return True
# Check negatively sloped diagonals
for row in range(3, 6):
for col in range(4):
if board[row][col] == piece and board[row - 1][col + 1] == piece and board[row - 2][
col + 2] == piece and board[row - 3][col + 3] == piece:
return True
return False
# not used now in this class
def check_sequence_in_whole_board(self, board: np.ndarray, piece: int, seq_len: int) -> bool:
"""
Overview:
Checks if a sequence of the bot's pieces of a given length can be formed anywhere on the current game board.
Arguments:
- board(:obj:`int`): The current game board.
- piece(:obj:`int`): The piece of the bot.
- seq_len(:obj:`int`): The length of the sequence.
Returns:
- result(:obj:`bool`): True if such a sequence can be formed; False otherwise.
"""
# Check horizontal locations
for row in range(6):
row_array = list(board[row, :])
for c in range(8 - seq_len):
window = row_array[c:c + seq_len]
if window.count(piece) == seq_len:
return True
# Check vertical locations
for col in range(7):
col_array = list(board[:, col])
for r in range(7 - seq_len):
window = col_array[r:r + seq_len]
if window.count(piece) == seq_len:
return True
# Check positively sloped diagonals
for row in range(6 - seq_len):
for col in range(7 - seq_len):
window = [board[row + i][col + i] for i in range(seq_len)]
if window.count(piece) == seq_len:
return True
# Check negatively sloped diagonals
for row in range(seq_len - 1, 6):
for col in range(7 - seq_len):
window = [board[row - i][col + i] for i in range(seq_len)]
if window.count(piece) == seq_len:
return True
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