last_double_first.py

#!/usr/bin/python
# brute force solution for https://www.youtube.com/watch?v=1lHDCAIsyb8

def reverse(number):
	s_number = str(number)
	l_number = len(s_number)
	return(int(s_number[l_number-1:] + s_number[:l_number-1]))
correct = 105263157894736842 # yeah...that brute force might took longer than I expected :)
print("Correct solution: %i, reversed: %i or doubled: %i." % (correct, reverse(correct), correct*2))
#i = 1 # it was immediately shown that the solution works with i=0 :)
i = 105263157884736842  # if I nudge it a bit towards a solution, it spits out the correct answer in a short time.
try:
	while 2*i != reverse(i):
		i = i + 1
except KeyboardInterrupt:
	print("Keyboard interrupt. Current i: %i" % i)
	raise
print("Number %i, reverse %i" % (i, reverse(i)))