Description

Your task is to imitate a turn-based variation of the popular "Snake" game.

You are given the initial configuration of the board and a list of commands which the snake follows one-by-one. The game ends if one of the following happens:

• the snake tries to eat its tail
• the snake tries to move out of the board
• it executes all the given commands.

Output the board configuration after the game ends. With the snake replaced by 'X' if the game ends abnormally.

Examples

input:
snakeGame([['.', '.', '.', '.'],
           ['.', '.', '<', '*'],
           ['.', '.', '.', '*']],
          "FFFFFRFFRRLLF")

output:
          [['.', '.', '.', '.'],
           ['X', 'X', 'X', '.'],
           ['.', '.', '.', '.']]

input:
snakeGame([['.', '.', '^', '.', '.'],
           ['.', '.', '*', '*', '.'],
           ['.', '.', '.', '*', '*']],
          "RFRF")

output:
          [['.', '.', 'X', 'X', '.'],
           ['.', '.', 'X', 'X', '.'],
           ['.', '.', '.', 'X', '.']]

input:
snakeGame([['.', '.', '*', '>', '.'],
           ['.', '*', '*', '.', '.'],
           ['.', '.', '.', '.', '.']],
          "FRFFRFFRFLFF")

output:
          [['.', '.', '.', '.', '.'],
           ['<', '*', '*', '.', '.'],
           ['.', '.', '*', '.', '.']]

Code

def snakeGame(gameBoard, commands):
    heads = {'v': (1, 0), '^': (-1, 0), '<': (0, -1), '>': (0, 1)}
    new_direc = {'v': {'L': '>', 'R': '<'}, 
                 '^': {'L': '<', 'R': '>'},                 
                 '<': {'L': 'v', 'R': '^'}, 
                 '>': {'L': '^', 'R': 'v'}}
    
    def find_snake():
        def get_next(x, y):
            for key, direc in heads.items():
                new_x, new_y = x + direc[0], y + direc[1]
                if new_x in range(len(gameBoard)) and new_y in range(len(gameBoard[0])):
                    if (new_x, new_y) not in snake:
                        if gameBoard[new_x][new_y] == '*':
                            return (new_x, new_y)

        # Get the head and the next body opposite of snake's direction
        snake = []
        for i, row in enumerate(gameBoard):
            for head in heads:
                if head in row:
                    snake.append((i, row.index(head)))
                    snake.append((snake[0][0] + heads[head][0] * -1, snake[0][1]  + heads[head][1] * -1))
        
        # Append the rest of the body
        while True:
            n = get_next(snake[-1][0], snake[-1][1])            
            if n is None:
                break
            snake.append(n)
        
        return snake
    
    def move_snake(snake):
        head = gameBoard[snake[0][0]][snake[0][1]]
        new_x, new_y = snake[0][0] + heads[head][0], snake[0][1]  + heads[head][1]
        new_snake = []
        if new_x in range(len(gameBoard)) and new_y in range(len(gameBoard[0])) and (new_x, new_y) not in snake:
            new_snake.append((new_x, new_y))
            
            for pos in snake[:-1]:
                new_snake.append(pos)
                
            return new_snake
             
    # Find starting snake
    snake = find_snake()
    
    for command in commands:   
        if command in "LR":
            # Change the head
            gameBoard[snake[0][0]][snake[0][1]] = new_direc[gameBoard[snake[0][0]][snake[0][1]]][command]
        else:
            temp = move_snake(snake)
            
            # if not valid move return dead snake
            if temp is None:
                for pos in snake:
                    x, y = pos
                    gameBoard[x][y] = 'X'
                return gameBoard
            
            # else move snake
            for a, b in zip(snake, temp):
                gameBoard[b[0]][b[1]] = gameBoard[a[0]][a[1]]
                
            gameBoard[snake[-1][0]][snake[-1][1]] = '.'
            snake = temp
    
    return gameBoard