Creation of all unique crosswords

Question

I want to generate all unique crosswords with a specific grid size (4x4 is a good size). All possible puzzles, including unique puzzles, are represented by a binary string with the length of the grid area (16 in the case of 4x4), so all possible 4x4 puzzles are represented by the binary forms of all numbers in the range 0 to 2 ^ 16.

It's easy to create them, but I'm curious if anyone has a good solution on how to programmatically eliminate incorrect and duplicate cases. For example, all puzzles with one column or one row are functionally identical, therefore, excluding 7 of these 8 cases. In addition, in accordance with the crossword puzzle symbols, all squares must be adjacent. I had success by removing all duplicate structures, but my decision took several minutes to execute and probably was not ideal. I am at a loss how to find contact, so if anyone has ideas on this, it will be very helpful.

I would prefer solutions in python, but I will write in any other language that you prefer. If anyone wants to, I can publish my Python code to generate all meshes and remove duplicates, as if slow.

Answer 1

Disclaimer: in most cases, unverified, different from all tests, have an effect by filtering out some gratings, and some spotty errors have been fixed. Of course, you can optimize.

def is_valid_grid (n):
    row_mask = ((1 << n) - 1)
    top_row  = row_mask << n * (n - 1)

    left_column  = 0
    right_column = 0

    for row in range (n):
        left_column  |= (1 << (n - 1)) << row * n
        right_column |= 1 << row * n

    def neighborhood (grid):
        return (((grid   & ~left_column)  << 1)
                | ((grid & ~right_column) >> 1)
                | ((grid & ~top_row)      << n)
                | (grid                   >> n))

    def is_contiguous (grid):
        # Start with a single bit and expand with neighbors as long as
        # possible.  If we arrive at the starting grid then it is
        # contiguous, else not.
        part = (grid ^ (grid & (grid - 1)))
        while True:
            expanded = (part | (neighborhood (part) & grid))
            if expanded != part:
                part = expanded
            else:
                break

        return part == grid

    def flip_y (grid):
        rows = []
        for k in range (n):
            rows.append (grid & row_mask)
            grid >>= n

        for row in rows:
            grid = (grid << n) | row

        return grid

    def rotate (grid):
        rotated = 0
        for x in range (n):
            for y in range (n):
                if grid & (1 << (n * y + x)):
                    rotated |= (1 << (n * x + (n - 1 - y)))

        return rotated

    def transform (grid):
        yield flip_y (grid)

        for k in range (3):
            grid = rotate (grid)
            yield grid
            yield flip_y (grid)

    def do_is_valid_grid (grid):
        # Any square in the topmost row?
        if not (grid & top_row):
            return False

        # Any square in the leftmost column?
        if not (grid & left_column):
            return False

        # Is contiguous?
        if not is_contiguous (grid):
            return False

        # Of all transformations, we pick only that which gives the
        # smallest number.
        for transformation in transform (grid):
            # A transformation can produce a grid without a square in the topmost row and/or leftmost column.
            while not (transformation & top_row):
                transformation <<= n

            while not (transformation & left_column):
                transformation <<= 1

            if transformation < grid:
                return False

        return True

    return do_is_valid_grid

def valid_grids (n):
    do_is_valid_grid = is_valid_grid (n)
    for grid in range (2 ** (n * n)):
        if do_is_valid_grid (grid):
            yield grid

for grid in valid_grids (4):
    print grid