def _alpha_beta(board: Connect4, depth: int, alpha: int, beta: int,
is_maximising_player: bool, player: bool):
if depth == 0:
return board.value # Opposing player has the current turn
if board.is_game_over:
return board.value - depth
if is_maximising_player:
score = LOW_BOUND
for move in board.legal_moves:
board.make_move(move)
score = max(
_alpha_beta(board, depth - 1, alpha, beta,
not is_maximising_player, player), score)
alpha = max(alpha, score)
board.unmake_move()
if alpha >= beta:
return score
else:
score = HIGH_BOUND
for move in board.legal_moves:
board.make_move(move)
score = min(
_alpha_beta(board, depth - 1, alpha, beta,
not is_maximising_player, player), score)
beta = min(beta, score)
board.unmake_move()
if alpha >= beta:
return score
return score
def _minimax(board: Connect4, depth: int, is_maximising_player: bool,
player: bool):
if depth == 0:
return board.value
if board.is_game_over:
return board.value - depth
if is_maximising_player:
score = LOW_BOUND
for move in board.legal_moves:
board.make_move(move)
score = max(
_minimax(board, depth - 1, not is_maximising_player, player),
score)
board.unmake_move()
else:
score = HIGH_BOUND
for move in board.legal_moves:
board.make_move(move)
score = min(
_minimax(board, depth - 1, not is_maximising_player, player),
score)
board.unmake_move()
return score
def _json_board(board: Connect4, params: Optional[Dict] = None):
by_rank = {}
for slot in SLOTS_VFLIP:
rank = int(slot / 7)
file = slot % 7
by_rank[rank] = by_rank.get(rank, [])
_square = {
'rank': rank,
'file': file,
'index': int(slot),
}
piece = board.piece_at(slot)
if piece:
_square['piece'] = 'red' if piece.colour else 'yellow'
by_rank[rank].append(_square)
by_rank_reverse = {}
for i, rank in enumerate(sorted(by_rank.keys(), reverse=True)):
by_rank_reverse[i] = by_rank[rank]
payload = {
'game': by_rank_reverse,
'turn': board.turn_name,
'mhn': board.mhn
}
if params:
payload.update(params)
return payload
def minimax(board: Connect4, depth: int):
score = LOW_BOUND
best_move = None
player = board.turn # Current player is the AI player
for move in board.legal_moves:
board.make_move(move)
value = _minimax(board, depth - 1, True, player)
board.unmake_move()
if not player:
value *= -1
if value >= score:
score = value
best_move = move
return best_move
def c4_new_game():
data = request.get_json()
c4 = Connect4()
cache['game'] = c4
if not data['player']:
return c4_make_move_ai() # Make first move
return _json_board(c4)
from flask import request
from typing import Optional, Dict
from connect_4.game import Connect4, IllegalMove, SLOTS_VFLIP
from connect_4.ai import minimax, alpha_beta
from web.server import app
cache = {
'game': Connect4(),
}
def _end_message(result: int) -> str:
if result == 1:
return 'Game over: Red wins!'
elif result == -1:
return 'Game over: Yellow wins!'
elif result == 0:
return 'Game over: Draw'
def _json_board(board: Connect4, params: Optional[Dict] = None):
by_rank = {}
for slot in SLOTS_VFLIP:
rank = int(slot / 7)
file = slot % 7
by_rank[rank] = by_rank.get(rank, [])
_square = {
'rank': rank,