adventOfCode/challenges/2024/06-guardGallivant/README.md

Day 6: Guard Gallivant

Part 2 is:

• higher than 456
• less than 1689

The first implementation of part 2 took 15 minutes to run.

• Turning visited_sequence in trace into a set instead of a list cut this to 60 seconds
• Starting immediately in front of the new obstacle when testing positions to put said new obstacle in cut this to 20 seconds
• Removing a load of maps and type wranging to turn the fully generic gridutil.add (and counterparts) into a more limited but much faster function took this to ~16 seconds

Before:

def _coordmap(a: AnyCoordinate, b: AnyCoordinate, fn: Callable) -> AnyCoordinate:
    at = type(a)
    return at(*map(fn, zip(a, b)))

def add(a: AnyCoordinate, b: AnyCoordinate) -> AnyCoordinate:
    return _coordmap(a, b, lambda x: x[0] + x[1])

After:

def add(a: Coordinate, b: Coordinate) -> Coordinate:
    return Coordinate(a.x + b.x, a.y + b.y)