advent-of-code/2024/17/two_bf.py
2024-12-25 12:59:49 +01:00

126 lines
3.2 KiB
Python

#!/usr/bin/env python3
import sys
import rich.progress
input_file = sys.argv[1]
with open(input_file) as fd:
lines = [line.rstrip() for line in fd.readlines()]
# program 3 bits numbers
# registers A, B, C: any int
# instruction 3 bits, operand 3 bits
# literal operand, combo operand: 0-3 literal, 4-6: register A,B,C
# instruction pointer starts at 0
# 0 adv: truncated division, numerator = A, denominator 2**combo operand -> A
# 1 bxl: bitwise XOR, B ^ literal operand -> B
# 2 bst: combo operand % 8 -> B
# 3 jnz: { A = 0: nothing; A != 0: literal operand -> IP } # no increase there!
# 4 bxc: bitwise XOR, B ^ C -> B # operand ignored
# 5 out: combo operand % 8 -> output
# 6 bdv: truncated division, numerator = A, denominator 2**combo operand -> B
# 7 cdv: truncated division, numerator = A, denominator 2**combo operand -> C
instnames = ["adv", "bxl", "bst", "jnz", "bxc", "out", "bdv", "cdv"]
oA = int(lines[0].split(":")[1])
oB = int(lines[1].split(":")[1])
oC = int(lines[2].split(":")[1])
program = [int(p) for p in lines[4].split(":")[1].split(",")]
def test(oA: int) -> bool:
# print(32, "Testing", A)
ip = 0
A = oA
B = oB
C = oC
# output: list[int] = list()
oi = 0
# jumped: set[tuple[int, int, int, int]] = set()
while ip in range(len(program)):
inst = program[ip]
liop = program[ip + 1]
# print(50, ip, instnames[inst], liop)
if inst == 1:
B = B ^ liop
elif inst == 3:
if A != 0:
ip = liop
# Infinite loop prevention
# state = (ip, A, B, C)
# # print(66, state, jumped)
# if state in jumped:
# print("Infinite loop!")
# return False
# jumped.add(state)
continue
elif inst == 4:
B = B ^ C
else:
coop = liop
if liop == 4:
coop = A
elif liop == 5:
coop = B
elif liop == 6:
coop = C
if inst == 2:
B = coop % 8
elif inst == 5:
ou = coop % 8
# output.append(ou)
if oi >= len(program) or program[oi] != ou:
# if len(output) >= 6:
# print(84, oA, output)
return False
oi += 1
else:
trunc_div = A // 2**coop
if inst == 0:
A = trunc_div
elif inst == 6:
B = trunc_div
elif inst == 7:
C = trunc_div
else:
raise NotImplementedError()
ip += 2
return oi == len(program)
# return output == program
# print(program)
# for i in range(0, len(program), 2):
# inst = program[i]
# liop = program[i + 1]
# print(106, i, instnames[inst], liop)
# print()
#
# print(test(100000000))
Amin = 2**(3*(len(program)-1))
Amax = 2**(3*len(program))
for A in rich.progress.track(range(Amin, Amax+1)):
if test(A):
print(A)
break
A += 1
# print(",".join([str(o) for o in output]))