In [1]:

import aocd

data = aocd.get_data(day=5, year=2017)
instructions = list(map(int, data.splitlines()))

In [2]:

def execute(instructions, decrement_at_3=False):
    pos = 0
    steps = 0
    while 0 <= pos < len(instructions):
        delta = instructions[pos]
        if (not decrement_at_3) or delta < 3:
            instructions[pos] += 1
        else:
            instructions[pos] -= 1
        pos += delta
        steps += 1
    return steps

In [3]:

assert execute([0, 3, 0, 1, -3]) == 5
print("Part 1:", execute(instructions[:]))

Part 1: 372671

In [4]:

assert execute([0, 3, 0, 1, -3], True) == 10
print("Part 2:", execute(instructions[:], True))

Part 2: 25608480