201817.py

import re
import sys
from collections import defaultdict

sys.setrecursionlimit(10000)

clay = defaultdict(bool)
settled, flowing = set(), set()

with open("201817.txt", "r") as f:
    for line in f.readlines():
        a, b, c = map(int, re.findall(r"\d+", line))
        if line.startswith("x="):
            for y in range(b, c + 1):
                clay[a + y * 1j] = True
        else:
            for x in range(b, c + 1):
                clay[x + a * 1j] = True

yl = [p.imag for p in clay]
ymin, ymax = min(yl), max(yl)
print("ymin", "ymax", ymin, ymax, "clay fields", len(clay))


def fill(p, direction=1j):
    flowing.add(p)
    below, left, right = p + 1j, p - 1, p + 1

    if not clay[below]:
        if below not in flowing and 1 <= below.imag <= ymax:
            fill(below)
        if below not in settled:
            return False

    l_filled = clay[left] or left not in flowing and fill(left, direction=-1)
    r_filled = clay[right] or right not in flowing and fill(right, direction=1)
    # print("left_right_filled", left_filled, right_filled)

    if direction == 1j and l_filled and r_filled:
        settled.add(p)

        while left in flowing:
            settled.add(left)
            left -= 1

        while right in flowing:
            settled.add(right)
            right += 1

    return (
        direction == -1
        and (l_filled or clay[left])
        or direction == 1
        and (r_filled or clay[right])
    )


fill(500)

print("Part One:", len([pt for pt in flowing | settled if ymin <= pt.imag <= ymax]))
print("Part Two:", len([pt for pt in settled if ymin <= pt.imag <= ymax]))