A class for generating snail matrices.

SnailMatrixGenerator.py

type Matrix = list[list[int]]


"""
This class is responsible for generating snail matrices of dimensions n * n.
"""
class SnailMatrixGenerator:
    """
    Constructs this generator.
    """
    def __init__(self, n):
        self.n = n
        self.matrix = [[0] * n for _ in range(n)]
        self.deltas = [(1, 0), (0, 1), (-1, 0), (0, -1)]
        self.delta_index = 0
        self.current_coordinate_x = 0
        self.current_coordinate_y = 0

    """
    Sets the given value at the current cursor location.
    """
    def set_value_at_cursor(self, value):
        self.matrix[self.current_coordinate_y][self.current_coordinate_x] = value

    """
    Moves the current cursor location to the next valid position.
    """
    def move_cell_cursor_to_next_location(self):
        save_cx = self.current_coordinate_x
        save_cy = self.current_coordinate_y

        while True:
            x = save_cx + self.deltas[self.delta_index][0]
            y = save_cy + self.deltas[self.delta_index][1]

            if self.check_current_coordinate_is_valid(x, y):
                self.current_coordinate_x = x
                self.current_coordinate_y = y
                return

            self.get_next_direction()

    """
    Makes sure that (x, y) is within the matrix and is not yet set.
    """
    def check_current_coordinate_is_valid(self, x, y):
        # Here, the only possible range for x is [-1, self.n].
        if x == -1 or x == self.n:
            return False

        # Here, the only possible range for y is [-1, self.n].
        if y == -1 or y == self.n:
            return False

        # Make sure that the current position is not yet set:
        return self.matrix[y][x] == 0

    """
    Changes the current progression direction.
    """
    def get_next_direction(self):
        if self.delta_index == len(self.deltas) - 1:
            # Go wrap around:
            self.delta_index = 0
        else:
            # Just proceed to the next one:
            self.delta_index += 1

    """
    Generates the snail pattern matrix.
    """
    def generate(self):
        value = 1

        while True:
            self.set_value_at_cursor(value)

            if value == self.n * self.n:
                # Here, the matrix is full.
                return self.matrix

            value += 1
            # Move to the next cursor location:
            self.move_cell_cursor_to_next_location()

if __name__ == "__main__":
    def print_matrix(m: Matrix) -> None:
        padding = len(str(len(m) ** 2))
        for row in m:
            print(" ".join(f"{num:>{padding}}" for num in row))


    smg = SnailMatrixGenerator(4)
    m = smg.generate()
    print_matrix(m)