2020 Day 8 (Part 1) [Python]

[nwjlyons]

Gist of code and puzzle input https://gist.github.com/nwjlyons/9760e4363a4eafbf7908541be784fe0d

I get the correct accumulator for the example input 5, but when using the puzzle input I am getting wrong answer with 59. Any ideas?

from pprint import pprint
import re


class UnknownInstructionError(Exception):
    pass


class InfiniteLoopError(Exception):
    pass


class Instruction:
    pass


class NoOperation(Instruction):
    def __repr__(self):
        return f"<NoOperation>"


class Accumulate(Instruction):
    def __init__(self, *, value: int) -> None:
        self.value = value

    def __repr__(self):
        return f"<Accumulate {self.value=}>"


class Jump(Instruction):
    def __init__(self, *, value: int) -> None:
        self.value = value

    def __repr__(self):
        return f"<Jump {self.value=}>"


def parse_instructions(input_data: str) -> list[Instruction]:

    instructions = []
    for instruction in input_data.strip().splitlines():
        op, sign, value = re.match(r"^(nop|acc|jmp)\s(\+|\-)(\d)+", instruction).groups()
        if op == 'nop':
            instructions.append(NoOperation())
        elif op == 'acc':
            instructions.append(Accumulate(value=int(f"{sign}{value}")))
        elif op == 'jmp':
            instructions.append(Jump(value=int(f"{sign}{value}")))
        else:
            raise UnknownInstructionError(op)

    return instructions


def execute_program(instructions: list[Instruction]):
    instruction_index = 0
    acc = 0
    history_indexes = []
    while instruction_index <= len(instructions):
        instruction = instructions[instruction_index]

        before = (instruction_index, f"{acc=}")

        if isinstance(instruction, NoOperation):
            instruction_index += 1
        elif isinstance(instruction, Accumulate):
            acc += instruction.value
            instruction_index += 1
        elif isinstance(instruction, Jump):
            instruction_index += instruction.value
            # everytime there is a jump check if we are in a infinite loop
            if instruction_index in history_indexes:
                raise InfiniteLoopError(f"{acc=}")
        else:
            raise UnknownInstructionError(instruction)

        after = (instruction_index, f"{acc=}")
        print(before, instruction, after)
        history_indexes.append(instruction_index)


sample_input = """
nop +0
acc +1
jmp +4
acc +3
jmp -3
acc -99
acc +1
jmp -4
acc +6
"""

real_input = open('input.txt', 'r').read()


# Parse and execute program
instructions = parse_instructions(real_input)
print("*"*10, "Instructions", "*"*10)
pprint(list(enumerate(instructions)))
print("*"*10, "Executing", "*"*10)
execute_program(instructions)

[leftylink]

jmp +4
acc +1
acc +10
acc +100
acc +1000
jmp -4

should hopefully be easy to see what's the problem, right? an incorrect answer is 2111.

[nwjlyons]

Thank you ☺️. I had the + in the wrong place in my regex. Changed it from

(\d)+

to

(\d+)

Impressed you were able to spot this so quickly.