aoc2024day17.py

# === Parsing ===

with open("input.txt", "r") as f:
    register_a = int(f.readline().split()[-1])
    register_b = int(f.readline().split()[-1])
    register_c = int(f.readline().split()[-1])
    _ = f.readline()
    program = [int(num) for num in f.readline().split()[-1].split(",")]

print(program, register_a, register_b, register_c)


# === Part 1 ===
from functools import partial

A, B, C = 4, 5, 6
registers = [0, 1, 2, 3, register_a, register_b, register_c]
output = []

operators = [
    lambda o: registers[A] // pow(2, registers[o]),
    lambda o: registers[B] ^ o,
    lambda o: registers[o] % 8,
    lambda o: ...,
    lambda o: registers[B] ^ registers[C],
    lambda o: registers[o] % 8,
    lambda o: registers[A] // pow(2, registers[o]),
    lambda o: registers[A] // pow(2, registers[o]),
]

state_updates = [
    partial(registers.__setitem__, A),
    partial(registers.__setitem__, B),
    partial(registers.__setitem__, B),
    lambda o: ...,
    partial(registers.__setitem__, B),
    output.append,
    partial(registers.__setitem__, B),
    partial(registers.__setitem__, C),
]

jumps = [
    lambda ptr, o: ptr + 2,
    lambda ptr, o: ptr + 2,
    lambda ptr, o: ptr + 2,
    lambda ptr, o: ptr + 2 if registers[A] == 0 else o,
    lambda ptr, o: ptr + 2,
    lambda ptr, o: ptr + 2,
    lambda ptr, o: ptr + 2,
    lambda ptr, o: ptr + 2,
]


ptr = 0
while ptr < len(program):
    opcode = program[ptr]
    operand = program[ptr + 1]
    value = operators[opcode](operand)
    state_updates[opcode](value)
    ptr = jumps[opcode](ptr, operand)

print(output)


# === Part 2 ===


def b(a):
    a_mod8 = a % 8
    return (a_mod8 ^ (a // pow(2, a_mod8 ^ 7))) % 8


found = []
to_explore = [(0, 0)]  # Pairs of A and number of matches made
while to_explore:
    a_, matches_made = to_explore.pop()
    if matches_made == len(program):
        found.append(a_)
        continue

    target_b = program[-(matches_made + 1)]
    for a in range(8 * a_, 8 * a_ + 8):
        if b(a) == target_b:
            to_explore.append((a, matches_made + 1))

print(sorted(found))