Solution to 538 Riddler "What are these dang bits!"

plot_bits.py

from matplotlib import pyplot as plt
import numpy as np
from sys import argv

def f(x,y):
    '''
    Count the number of iterations for Euclid's algorithm computing gcd(x,y),
    and return whether it is odd or even.
    '''
    iters = 0
    while 0 not in (x,y):
        iters += 1
        if x < y:
            y = y-x
        else:
            x = x-y
            
    return iters % 2

def build_array(dim):
    '''
    Build a dim x dim array of the values of f(i,j)
    '''
    rtn = np.ndarray((dim, dim), dtype=int)
    for i in range(dim):
        for j in range(dim):
            rtn[i,j] = f(i,j)

    return rtn
            
def main():
    if len(argv) < 2:
        raise ValueError("Pass desired dimension as first command line arg")

    dim = int(argv[1])

    ary = build_array(dim)

    plt.imshow(ary)
    plt.gca().invert_yaxis()
    plt.show()

if __name__ == '__main__':
    main()