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‎Backtracking/tic_tac_toe_game.py

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'''
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TIC-TAC-TOE GAME USING MINIMAX ALGORITHM
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Minimax is a kind of backtracking algorithm. It searches, recursively, the
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best move that leads the Max player to win or not lose (draw). It considers
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the current state of the game and the available moves at that state, then
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for each valid move, it plays (alternating min and max) until it finds a
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terminal state (win, draw or lose).
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'''
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#Import the necessary libraries
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import numpy as np
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from math import inf as infinity
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#Set the Empty Board
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game_state = [[' ',' ',' '],
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[' ',' ',' '],
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[' ',' ',' ']]
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#Create the Two Players as 'X'/'O'
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players = ['X','O']
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#Method for checking the correct move on Tic-Tac-Toe
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def play_move(state, player, block_num):
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if state[int((block_num-1)/3)][(block_num-1)%3] is ' ':
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state[int((block_num-1)/3)][(block_num-1)%3] = player
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else:
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block_num = int(input("Block is not empty, ya blockhead! Choose again: "))
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play_move(state, player, block_num)
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#Method to copy the current game state to new_state of Tic-Tac-Toe
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def copy_game_state(state):
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new_state = [[' ',' ',' '],[' ',' ',' '],[' ',' ',' ']]
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for i in range(3):
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for j in range(3):
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new_state[i][j] = state[i][j]
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return new_state
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#Method to check the current state of the Tic-Tac-Toe
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def check_current_state(game_state):
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# Check horizontals in first row
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if (game_state[0][0] == game_state[0][1] and game_state[0][1] == game_state[0][2] and game_state[0][0] is not ' '):
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return game_state[0][0], "Done"
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# Check horizontals in second row
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if (game_state[1][0] == game_state[1][1] and game_state[1][1] == game_state[1][2] and game_state[1][0] is not ' '):
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return game_state[1][0], "Done"
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# Check horizontals in third row
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if (game_state[2][0] == game_state[2][1] and game_state[2][1] == game_state[2][2] and game_state[2][0] is not ' '):
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return game_state[2][0], "Done"
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# Check verticals in first column
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if (game_state[0][0] == game_state[1][0] and game_state[1][0] == game_state[2][0] and game_state[0][0] is not ' '):
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return game_state[0][0], "Done"
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# Check verticals in second column
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if (game_state[0][1] == game_state[1][1] and game_state[1][1] == game_state[2][1] and game_state[0][1] is not ' '):
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return game_state[0][1], "Done"
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# Check verticals in third column
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if (game_state[0][2] == game_state[1][2] and game_state[1][2] == game_state[2][2] and game_state[0][2] is not ' '):
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return game_state[0][2], "Done"
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# Check left diagonal
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if (game_state[0][0] == game_state[1][1] and game_state[1][1] == game_state[2][2] and game_state[1][1] is not ' '):
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return game_state[1][1], "Done"
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# Check right diagonal
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if (game_state[0][2] == game_state[1][1] and game_state[1][1] == game_state[2][0] and game_state[0][2] is not ' '):
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return game_state[1][1], "Done"
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draw_flag = 0
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for i in range(3):
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for j in range(3):
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if game_state[i][j] is ' ':
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draw_flag = 1
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if draw_flag is 0:
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return None, "Draw"
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return None, "Not Done"
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#Method to print the Tic-Tac-Toe Board
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def print_board(game_state):
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print('----------------')
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print('| ' + str(game_state[0][0]) + ' || ' + str(game_state[0][1]) + ' || ' + str(game_state[0][2]) + ' |')
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print('----------------')
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print('| ' + str(game_state[1][0]) + ' || ' + str(game_state[1][1]) + ' || ' + str(game_state[1][2]) + ' |')
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print('----------------')
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print('| ' + str(game_state[2][0]) + ' || ' + str(game_state[2][1]) + ' || ' + str(game_state[2][2]) + ' |')
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print('----------------')
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#Method for implement the Minimax Algorithm
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def getBestMove(state, player):
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winner_loser , done = check_current_state(state)
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# Checking condition for winner, if winner_loser is 'O' then Computer won
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# else if winner_loser is 'X' then You won else game is draw
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if done == "Done" and winner_loser=='O':
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return 1 # for computer
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elif done == "Done" and winner_loser=='X':
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return -1 # for player
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elif done == "Draw":
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return 0
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moves = []
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empty_cells = []
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#Append the block_num to the empty_cells list
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for i in range(3):
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for j in range(3):
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if state[i][j] is ' ':
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empty_cells.append(i*3 + (j+1))
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for empty_cell in empty_cells:
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move = {}
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move['index'] = empty_cell
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#Call the copy_game_state method
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new_state = copy_game_state(state)
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\
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play_move(new_state, player, empty_cell)
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#if player is computer
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if player == 'O':
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result = getBestMove(new_state,'X')
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move['score'] = result
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else:
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result = getBestMove(new_state,'O')
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move['score'] = result
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moves.append(move)
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# Find best move
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best_move = None
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#Check if player is computer('O')
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if player=='O':
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best = -infinity
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for move in moves:
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if move['score']>best:
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best = move['score']
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best_move = move['index']
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else:
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best = infinity
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for move in moves:
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if move['score']<best:
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best = move['score']
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best_move = move['index']
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return best_move
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# Now PLaying the Tic-Tac-Toe Game
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play_again = 'Y'
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while play_again == 'Y' or play_again == 'y':
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#Set the empty board for Tic-Tac-Toe
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game_state = [[' ',' ',' '],
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[' ',' ',' '],
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[' ',' ',' ']]
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#Set current_state as "Not Done"
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current_state = "Not Done"
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print("\nNew Game!")
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#print the game_state
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print_board(game_state)
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#Select the player_choice to start the game
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player_choice = input("Choose which player goes first - X(You) or O(Computer): ")
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#Set winner as None
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winner = None
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#if player_choice is ('X' or 'x') for humans else for computer
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if player_choice == 'X' or player_choice == 'x':
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current_player_idx = 0
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else:
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current_player_idx = 1
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while current_state == "Not Done":
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#For Human Turn
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if current_player_idx == 0:
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block_choice = int(input("Your turn please! Choose where to place (1 to 9): "))
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play_move(game_state, players[current_player_idx], block_choice)
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else: # Computer turn
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block_choice = getBestMove(game_state, players[current_player_idx])
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play_move(game_state, players[current_player_idx], block_choice)
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print("AI plays move: " + str(block_choice))
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print_board(game_state)
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winner, current_state = check_current_state(game_state)
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if winner is not None:
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print(str(winner) + " won!")
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else:
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current_player_idx = (current_player_idx + 1)%2
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if current_state is "Draw":
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print("Draw!")
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play_again = input('Wanna try again?(Y/N) : ')
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if play_again == 'N':
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print('Thank you for playing Tic-Tac-Toe Game!!!!!!!')
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'''
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Sample woking:
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New Game!
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----------------
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| || || |
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----------------
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| || || |
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----------------
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| || || |
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----------------
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Choose which player goes first - X(You) or O(Computer): X
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Your turn please! Choose where to place (1 to 9): 3
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----------------
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| || || X |
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----------------
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| || || |
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----------------
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| || || |
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----------------
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AI plays move: 2
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----------------
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| || O || X |
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----------------
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| || || |
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----------------
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| || || |
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----------------
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Your turn please! Choose where to place (1 to 9): 7
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----------------
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| || O || X |
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----------------
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| || || |
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----------------
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| X || || |
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----------------
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AI plays move: 1
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----------------
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| O || O || X |
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----------------
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| || || |
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----------------
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| X || || |
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----------------
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Your turn please! Choose where to place (1 to 9): 5
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----------------
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| O || O || X |
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----------------
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| || X || |
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----------------
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| X || || |
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----------------
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X won!
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Wanna try again?(Y/N) : n
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'''

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