Direct translation from .e1 original

aoc2025_day9part2.py

from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
import sys

@dataclass
class Point:
    x: int
    y: int

@dataclass
class Border:
    bx: int
    up: bool

@dataclass
class Rect:
    a: int
    b: int
    area: int

def parse_int_or(s: str, default: int) -> int:
    try:
        return int(s)
    except ValueError:
        return default

def by_line(text: str) -> list[str]:
    if text == "":
        return []
    parts = text.split("\n")
    if parts and parts[-1] == "":
        parts.pop()
    return parts

def to_points(line: str) -> Point:
    v = [parse_int_or(s, -1) for s in line.split(",")]
    return Point(v[0], v[1])

def area(points: list[Point], i: int, j: int) -> int:
    a = points[i]
    b = points[j]
    return (abs(a.x - b.x) + 1) * (abs(a.y - b.y) + 1)

def process_line(lst: list[Border]) -> list[Border]:
    arr = list(lst)
    arr.sort(key=lambda b: b.bx)
    return [arr[i] for i in range(len(arr)) if i == 0 or arr[i].up != arr[i - 1].up]

def fits(st: int, en: int, line: list[Border]) -> bool:
    return any(
        line[i].up
        and not line[i + 1].up
        and line[i].bx <= st
        and line[i + 1].bx >= en
        for i in range(len(line) - 1)
    )

def main() -> None:
    input_path = Path(sys.argv[1]) if len(sys.argv) > 1 else Path("input9t.txt")
    text = input_path.read_text() if input_path.exists() else ""
    points = [to_points(line) for line in by_line(text)]

    np = len(points)

    lines: list[list[Border]] = [[] for _ in range(100000)]

    def draw_vert_line(x: int, first: int, last: int, going_up: bool) -> None:
        for y in range(first, last + 1):
            lines[y].insert(0, Border(x, going_up))

    for i in range(np):
        j = (i + 1) % np
        pi = points[i]
        pj = points[j]
        going_up = pi.y > pj.y
        if pi.x == pj.x:
            draw_vert_line(pi.x, min(pi.y, pj.y), max(pi.y, pj.y), going_up)

    spans = [process_line(line) for line in lines]

    def rect_fits(r: Rect) -> bool:
        p1 = points[r.a]
        p2 = points[r.b]
        st = min(p1.x, p2.x)
        en = max(p1.x, p2.x)
        y0 = min(p1.y, p2.y)
        y1 = max(p1.y, p2.y)
        for y in range(y0, y1 + 1):
            if not fits(st, en, spans[y]):
                return False
        return True

    rects = [
        Rect(j, i + 1, area(points, j, i + 1))
        for i in range(np - 1)
        for j in range(i + 1)
    ]
    rects = [r for r in rects if rect_fits(r)]

    rects.sort(key=lambda r: r.area, reverse=True)
    print(rects[0].area)

if __name__ == "__main__":
    main()