Created
February 29, 2024 16:04
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#Instead of x and o players are 1 and -1 | |
def eval(board): #returns 1 if player 1 wins, 0 if no player wins, -1 if player -1 wins | |
for i in range(3): | |
if board[i*3] == board [i*3 + 1] == board[i*3 +2] and board[i*3]!=0: #Horizontal | |
return board[i*3] | |
if board[i] == board[i+3] == board [i+6] and board[i*3]!=0: #Vertical | |
return board[i] | |
if board[0] == board[4] == board[8] and board[0]!=0: #Diagonal 1 | |
return board[0] | |
if board[2] == board[4] == board[6] and board[2]!=0: #Diagonal 2 | |
return board[2] | |
return 0 #Otherwise | |
def moves(board): #Gets all possible moves by index 0-8 inclusive | |
mv = [] | |
for i in range(len(board)): | |
if (board[i] == 0): | |
mv.append(i) | |
return mv | |
def alphabeta(node, depth, a, b, player): | |
if len(moves(node)) == 0 or eval(node) !=0 or depth==9: #Terminal Conditions | |
return eval(node) | |
if player == 1: | |
value = -3 #Arbitrary, must be below -1 but doesn't really matter for tic tac toe. | |
for i in moves(node): #Try all moves | |
tboard = board.copy() | |
tboard[i] = player #Add move tp board | |
value = max(value, alphabeta(tboard, depth + 1, a, b, player*-1)) #Minimax type thing | |
if value > b: #Prune the tree | |
break | |
a = max(a, value) | |
return value | |
else: | |
value = 3 | |
for i in moves(node): | |
tboard = board.copy() | |
tboard[i] = player | |
value = min(value, alphabeta(tboard, depth + 1, a, b, player*-1)) | |
if value < a: | |
break | |
b = min(b, value) | |
return value | |
def ab_get_best_move(board,player): | |
t_score = -1 | |
best_move = moves(board)[0] | |
for i in moves(board): | |
tboard = board.copy() | |
tboard[i] = player | |
score = alphabeta(tboard,0,-2,2,-player) * player | |
if score > t_score: | |
best_move = i | |
t_score = score | |
return best_move,t_score | |
board = [1,-1,0, | |
1,-1,0, | |
0 ,0,0] | |
ab_get_best_move(board,1) |
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wow! amazing code