def show_nqueens(q: list[int]) -> str:
    '''
    >>> board = show_nqueens([0])
    >>> board
    'Q'
    >>> print(board)
    Q

    >>> board = show_nqueens([0, 1, 2, 3])
    >>> print(board)
    . . . Q
    . . Q .
    . Q . .
    Q . . .

    >>> board = show_nqueens([1, 3, 0, 2])
    >>> print(board)
    . Q . .
    . . . Q
    Q . . .
    . . Q .

    >>> board = show_nqueens([1, 3, 5, 0, 2, 4])
    >>> print(board)
    . . Q . . .
    . . . . . Q
    . Q . . . .
    . . . . Q .
    Q . . . . .
    . . . Q . .

    '''
    n = len(q)

    def row(i: int) -> list[str]:
        return ' '.join(['Q' if q[j] == i else '.' for j in range(n)])

    return '\\n'.join([row(i) for i in range(n - 1, -1, -1)])

import doctest
doctest.testmod()