aoc-2016/25.py

#!/usr/bin/python3

"""Solution for day 25 of Advent of Code 2016.

This is a copy of Day 23's solution, with an 'out' instruction added.

Manual testing showed the output repeats regularly, so we just run the program until there are 20 bits output.

TODO: Add a common class for handling the assembly code, as it's now repeated in 3 places.
"""

import itertools


def value(registers, x):
    try:
        return int(x)
    except ValueError:
        return registers[x]


def cpy(registers, src, dst):
    registers[dst] = value(registers, src)


def inc(registers, reg):
    registers[reg] += 1


def dec(registers, reg):
    registers[reg] -= 1


def jnz(registers, val, tar):
    registers['pc'] += 0 if value(registers, val) == 0 else value(registers, tar) - 1


def tgl(registers, ins):
    mappings = {inc: dec, dec: inc, tgl: inc, jnz: cpy, cpy: jnz}
    target = registers['pc'] + value(registers, ins)
    registers['in'][target] = (mappings[registers['in'][target][0]], registers['in'][target][1])


def out(registers, val):
    registers['out'].append(value(registers, val))


def try_multiply(registers):
    try:
        pc = registers['pc']
        chunk = registers['in'][pc:pc+6]
        instr, args = map(list, zip(*chunk))
        if instr == [cpy, inc, dec, jnz, dec, jnz] \
                and args[0][1] == args[2][0] == args[3][0] \
                and args[4][0] == args[5][0] \
                and args[1][0] != args[0][1] != args[4][0] != args[0][0] \
                and args[3][1] == '-2' and args[5][1] == '-5':
            registers[args[1][0]] += value(registers, args[0][0]) * value(registers, args[4][0])
            registers[args[2][0]] = 0
            registers[args[4][0]] = 0
            registers['pc'] += 5
            return True
    except:
        pass
    return False


def step(registers):
    if not try_multiply(registers):
        try:
            registers['in'][registers['pc']][0](registers, *registers['in'][registers['pc']][1])
        except:
            pass


def run(values):
    registers = values
    registers['pc'] = 0
    registers['out'] = []
    registers['in'] = instr.copy()

    while registers['pc'] < len(instr) and len(registers['out']) < 20:
        step(registers)
        registers['pc'] += 1

    return registers['out']


with open('data/25.txt', 'r') as file:
    instr = map(str.split, map(str.strip, file.readlines()))
    instr = [(globals()[i[0]], i[1:]) for i in instr]

for a in itertools.count():
    if run({'a': a, 'b': 0, 'c': 0, 'd': 0}) == [0, 1] * 10:
        print('Part one: %s' % a)
        break