Slow burner.
First part was a straightforward implementation
of a runner, the code is extracted to `org_version()`.
Part 2 was way more tricky. Like many others, trying
to understand the program felt necessary. This
intepretation is this:
"""Python version of puzzle input program."""
a = <unknown>
b, c = 0, 0
while a:
b = (a % 8) ^ 1
c = a // (2**b)
b = (b ^ 5) ^ c
a = a // (2**3)
print(b % 8)
Some clarification here:
- the value is octagonal. 1-8 is the key.
- The value of reg a is _high_. It is not meant to
be brute forced.
The idea, which is not originally mine, is to go
from right to left. This code can be used to try
out some patterns:
while True:
python_version(input("Provide A:"))
Here, it was apparent a=4 gives the last digit of
my puzzle input. a=37 (4 * 8 + 3) gives the last
2 digits. a=222 (37 * 8 + 6) gives the last 3
digits, and so on.
Knowing the program could be reconstructed like
this, the first code halted at wrong values. Turns
out some steps give more than 1 possible scenario.
The code was therefore in need of a queue.
Anders Englöf Ytterström
14520a4625