Point example and AoC 2022-09

point.py

from dataclasses import dataclass

@dataclass(frozen=True)
class Point:
    x: float
    y: float

    def __repr__(self):
        return f"({self.x},{self.y})"

    def __add__(p, q):
        return Point(p.x + q.x, p.y + q.y)

solve.py

from point import Point
from itertools import accumulate, chain
from math import copysign


def sign(n):
    return 0 if n == 0 else int(copysign(1, n))


def step(h, t):
    if abs(h.x - t.x) > 1 or abs(h.y - t.y) > 1:
        return t + Point(sign(h.x - t.x), sign(h.y - t.y))
    return t


def chains(xs, ys):
    return chain.from_iterable([xs, ys])


def solve(path, length):
    tail = [Point(0, 0)] * length
    trail = set()
    for h in path:
        for i, (p, q) in enumerate(zip(chains([h], tail), tail)):
            tail[i] = step(p, q)
        trail.add(tail[-1])
    return len(trail)


dirs = {
    "U": Point(0, 1),
    "R": Point(1, 0),
    "D": Point(0, -1),
    "L": Point(-1, 0),
}

points = []
for (d, c) in map(str.split, open("input").read().splitlines()):
    points.extend([dirs[d]] * int(c))

path = list(accumulate(points))

print(solve(path, 1))
print(solve(path, 9))