Nested loops: print pattern (spiral numbers)

Problem: Print the following pattern for a given n (e.g. n=5 below). Number starts at 0 and after reaching 9, it resets to 0.


0 1 2 3 4
5 6 7 8 5
4 3 0 9 6
3 2 1 0 7
2 1 0 9 8

Solution in Python:

def print_pattern(n):

    """


    Author: Mayur P Srivastava

    n is number of colmns or rows.

    """

    matrix = create_matrix(n)

    x0  = -1

    y0  = -1

    num = 0

    

    for m in range(n, 0, -2):

        x0    += 1

        y0    += 1

        x      = 0

        y      = 0

        x_incr = 1

        y_incr = 0

        for i in range((m-1)*4):

            matrix[y+y0][x+x0] = num % 10

            if x+x_incr == m:

                x_incr = 0

                y_incr = 1

            if y+y_incr == m:

                x_incr = -1

                y_incr = 0

            if x+x_incr == -1:

                x_incr = 0

                y_incr = -1

            x   += x_incr

            y   += y_incr

            num += 1

    print "\n".join(" ".join(str(e) for e in row) for row in matrix)

def create_matrix(n, value=0):

    matrix = []

    for i in range(n):

        row = []

        for j in range(n):

            row.append(value)

        matrix.append(row)

    return matrix

Concepts learned: nested loops.