``````# Describes all sets of positive integers {x, y, z} such that
# x, y and z have no occurrence of 0,
# every nonzero digit occurs exactly once in one of x, y or z,
# and x, y and z are perfect squares.
# Encodes a set of digits as a natural number.
#
# Written by Eric Martin for COMP9021

from math import sqrt, ceil
from bit_set import set_encoding

def encoding_if_ok(number, encoded_number):
while number:
# Extract rightmost digit, d, from number
digit = number % 10
# Check that that d is not encoded in encoded_number
if 1 << digit & encoded_number:
return None
# Add encoding of d to encoded_number
encoded_number |= 1 << digit
# Get rid of rightmost digit of number
number //= 10
return encoded_number

# If it was a perfect square, max_square would, associated with 1 and 4,
# be the largest member of a possible solution. */
max_square = 9876532
nb_of_solutions = 0
limit = ceil(sqrt(max_square))
encoding_of_all_digits = set_encoding(set(range(10)))
for x in range(1, limit):
x_square = x * x
# encoded_0_and_x_square is not None
# iff all digits in x_square are distinct and not equal to 0
# (encoded as 1)
encoded_0_and_x_square = encoding_if_ok(x_square, 1)
if not encoded_0_and_x_square:
continue
for y in range(x + 1, limit):
y_square = y * y
# encoded_0_and_x_square_and_y_square is not None
# iff all digits in y_square are distinct, distinct to 0,
# and distinct to all digits in x_square
encoded_0_and_x_square_and_y_square =\
encoding_if_ok(y_square, encoded_0_and_x_square)
if not encoded_0_and_x_square_and_y_square:
continue
for z in range(y + 1, limit):
z_square = z * z
# encoded_0_and_x_square_and_y_square_and_z_square is not None
# iff all digits in z_square are distinct, distinct to 0,
# and distinct to all digits in x_square and y_square
encoded_0_and_x_square_and_y_square_and_z_square =\
encoding_if_ok(z_square, encoded_0_and_x_square_and_y_square)
if not encoded_0_and_x_square_and_y_square_and_z_square:
continue
if encoded_0_and_x_square_and_y_square_and_z_square !=\
encoding_of_all_digits:
continue
print('{:7d} {:7d} {:7d}'.format(x_square, y_square, z_square))
nb_of_solutions += 1
print('\nAltogether, {:} solutions have been found.'.format(nb_of_solutions))

``````

Resource created Wednesday 05 August 2015, 10:58:51 AM, last modified Wednesday 05 August 2015, 11:02:40 AM.

file: three_special_perfect_squares_v2.py