get_adjacent_matrices.py

def get_adjacent_matrices(matrix: Matrix, empty_tile: Tuple[int, int] = None) -> List[Matrix]:
    def find_empty_tile(matrix):
        for i in range(len(matrix)):
            for j in range(len(matrix[i])):
                if matrix[i][j] == 0:
                    return (i, j)

    if empty_tile is None:
        empty_tile = find_empty_tile(matrix)

    def get_candidates(row: int, col: int) -> List[Tuple[int, int]]:
        """
        ex 1, 1 => [(0, 1), (2, 1), (1, 0), (1, 2)]
        """
        return [(row - 1, col), (row + 1, col), (row, col - 1), (row, col + 1)]

    def filter_candidates(candidates: List[Matrix]) -> List[Matrix]:
        """
        matrix = [[1, 2], [3, 0]]
        ex  [(0, 1), (2, 1), (1, 0), (1, 2)] -> [(0, 1), (1, 0)]
        """
        new_list = []
        for (i, j) in candidates:
            if i < len(matrix) and i >= 0 and j < len(matrix[i]) and j >= 0:
                new_list.append((i, j))
        return new_list

    row_empty, col_empty = empty_tile
    candidates = get_candidates(row_empty, col_empty)
    new_empty_tiles = filter_candidates(candidates)

    neighbors = []
    for new_empty_tile in new_empty_tiles:
        neighbor = move_empty_tile(matrix, empty_tile, new_empty_tile)
        neighbors.append(neighbor)

    return neighbors