(A wall is outside if its entirely to the left OR entirely to the right of the rect) OR (entirely above OR entirely below).

   fn check_wall_outside(
        c: &(&Coord, &Coord),
        top: usize,
        bottom: usize,
        left: usize,
        right: usize,
    ) -> bool {
        if (c.0.x <= left && c.1.x <= left) || (c.0.x >= right && c.1.x >= right) {
            return true;
        }
        if (c.0.y <= top && c.1.y <= top) || (c.0.y >= bottom && c.1.y >= bottom) {
            return true;
        }
        false
    }

   #[test]
    fn test_y2025_day9_part2_mine1() {
        let input = include_str!("../../input/2025/day_9.txt");
        let coords = input
            .lines()
            .map(|l| {
                let halfs = l.split_once(',').unwrap();
                Coord {
                    x: halfs.0.parse::<usize>().unwrap(),
                    y: halfs.1.parse::<usize>().unwrap(),
                }
            })
            .collect::<Vec<Coord>>();

        let mut walls = vec![];

        for i in 0..coords.len() {
            let first = &coords[i];
            let second = coords.get(i + 1).unwrap_or(coords.first().unwrap());

            walls.push((first, second));
        }

        let mut max_area = 0;
        for i in 0..coords.len() {
            let first = &coords[i];
            'next_rect: for j in i..coords.len() {
                let second = &coords[j];
                if first == second {
                    continue 'next_rect;
                }
                let area = (first.x.abs_diff(second.x) + 1) * (first.y.abs_diff(second.y) + 1);
                if area < max_area {
                    continue 'next_rect;
                }

                let (top, bottom) = if first.y > second.y {
                    (second.y, first.y)
                } else {
                    (first.y, second.y)
                };

                let (left, right) = if first.x > second.x {
                    (second.x, first.x)
                } else {
                    (first.x, second.x)
                };

                for wall in &walls {
                    if !check_wall_outside(wall, top, bottom, left, right) {
                        continue 'next_rect;
                    }
                }

                max_area = area;
            }
        }
        assert_eq!(max_area, 1542119040);
        println!("Part 2: {}", max_area);
    }