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tic tac toe minimax

tarek zain answered on May 12, 2022 Popularity 10/10 Helpfulness 3/10
answer tic tac toe minimax
tic tac toe minimax

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# Python3 program to find the next optimal move for a player
player, opponent = 'x', 'o'
 
# This function returns true if there are moves
# remaining on the board. It returns false if
# there are no moves left to play.
def isMovesLeft(board) :
 
    for i in range(3) :
        for j in range(3) :
            if (board[i][j] == '_') :
                return True
    return False
 
# This is the evaluation function as discussed
# in the previous article ( http://goo.gl/sJgv68 )
def evaluate(b) :
   
    # Checking for Rows for X or O victory.
    for row in range(3) :    
        if (b[row][0] == b[row][1] and b[row][1] == b[row][2]) :       
            if (b[row][0] == player) :
                return 10
            elif (b[row][0] == opponent) :
                return -10
 
    # Checking for Columns for X or O victory.
    for col in range(3) :
      
        if (b[0][col] == b[1][col] and b[1][col] == b[2][col]) :
         
            if (b[0][col] == player) :
                return 10
            elif (b[0][col] == opponent) :
                return -10
 
    # Checking for Diagonals for X or O victory.
    if (b[0][0] == b[1][1] and b[1][1] == b[2][2]) :
     
        if (b[0][0] == player) :
            return 10
        elif (b[0][0] == opponent) :
            return -10
 
    if (b[0][2] == b[1][1] and b[1][1] == b[2][0]) :
     
        if (b[0][2] == player) :
            return 10
        elif (b[0][2] == opponent) :
            return -10
 
    # Else if none of them have won then return 0
    return 0
 
# This is the minimax function. It considers all
# the possible ways the game can go and returns
# the value of the board
def minimax(board, depth, isMax) :
    score = evaluate(board)
 
    # If Maximizer has won the game return his/her
    # evaluated score
    if (score == 10) :
        return score
 
    # If Minimizer has won the game return his/her
    # evaluated score
    if (score == -10) :
        return score
 
    # If there are no more moves and no winner then
    # it is a tie
    if (isMovesLeft(board) == False) :
        return 0
 
    # If this maximizer's move
    if (isMax) :    
        best = -1000
 
        # Traverse all cells
        for i in range(3) :        
            for j in range(3) :
              
                # Check if cell is empty
                if (board[i][j]=='_') :
                 
                    # Make the move
                    board[i][j] = player
 
                    # Call minimax recursively and choose
                    # the maximum value
                    best = max( best, minimax(board,
                                              depth + 1,
                                              not isMax) )
 
                    # Undo the move
                    board[i][j] = '_'
        return best
 
    # If this minimizer's move
    else :
        best = 1000
 
        # Traverse all cells
        for i in range(3) :        
            for j in range(3) :
              
                # Check if cell is empty
                if (board[i][j] == '_') :
                 
                    # Make the move
                    board[i][j] = opponent
 
                    # Call minimax recursively and choose
                    # the minimum value
                    best = min(best, minimax(board, depth + 1, not isMax))
 
                    # Undo the move
                    board[i][j] = '_'
        return best
 
# This will return the best possible move for the player
def findBestMove(board) :
    bestVal = -1000
    bestMove = (-1, -1)
 
    # Traverse all cells, evaluate minimax function for
    # all empty cells. And return the cell with optimal
    # value.
    for i in range(3) :    
        for j in range(3) :
         
            # Check if cell is empty
            if (board[i][j] == '_') :
             
                # Make the move
                board[i][j] = player
 
                # compute evaluation function for this
                # move.
                moveVal = minimax(board, 0, False)
 
                # Undo the move
                board[i][j] = '_'
 
                # If the value of the current move is
                # more than the best value, then update
                # best/
                if (moveVal > bestVal) :               
                    bestMove = (i, j)
                    bestVal = moveVal
 
    print("The value of the best Move is :", bestVal)
    print()
    return bestMove
# Driver code
board = [
    [ 'x', 'o', 'x' ],
    [ 'o', 'o', 'x' ],
    [ '_', '_', '_' ]
]
 
bestMove = findBestMove(board)
 
print("The Optimal Move is :")
print("ROW:", bestMove[0], " COL:", bestMove[1])
 
# This code is contributed by divyesh072019
Popularity 10/10 Helpfulness 3/10 Language python
Source: www.geeksforgeeks.org
Tags: minimax python tic-tac-toe
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Contributed on May 12 2022
tarek zain
0 Answers Avg Quality 2/10
tic tac toe minimax

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