aoc_day8_2020.py

def run_program(program):
    acc = 0
    pointer = 0
    seen = set()

    while pointer not in seen:
        op, value = program[pointer]
        seen.add(pointer)
        if op == 'nop':
            pointer += 1

        if op == 'acc':
            acc += value
            pointer += 1

        if op == 'jmp':
            pointer += value

        if op == 'ext':
            return True, acc

    return False, acc


program = [(op, int(value)) for op, value in [line.split(" ") for line in INPUT.split("\n")]]
program.append(('ext', 0))

# Part 1:
success, acc = run_program(program)
print(acc)

# Part 2:
for offset, (op, value) in enumerate(program):
    if op in ['jmp', 'nop']:
        program[offset] = ('nop' if op == 'jmp' else 'jmp', value)
        success, acc = run_program(program)
        if success:
            print(acc)
            break
        program[offset] = (op, value)