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|
use nom::{
bytes::complete::tag,
character::complete::{i32, line_ending},
combinator::map,
multi::separated_list1,
sequence::tuple,
IResult,
};
use std::{collections::BTreeSet, fs};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let input = fs::read_to_string("inputs/day_14.txt")?;
let room = Room::parser(&input).unwrap().1;
{
let mut void_room = room.clone();
let mut room_is_full = false;
while !room_is_full {
let drop_result = void_room.drop_sand(true);
room_is_full = drop_result != DropSandResult::Settled;
if drop_result == DropSandResult::RoomFull {
return Err("The room filled up to the top!".into());
}
}
dbg!(void_room.sand.len());
}
{
let mut floor_room = room.clone();
let mut room_is_full = false;
while !room_is_full {
let drop_result = floor_room.drop_sand(false);
room_is_full = drop_result != DropSandResult::Settled;
if drop_result == DropSandResult::FellIntoTheVoid {
return Err("This room shouldn't have a void!".into());
}
}
dbg!(floor_room.sand.len());
}
Ok(())
}
#[derive(Debug, Clone)]
struct Room {
walls: Vec<Wall>,
sand: BTreeSet<Point>,
sand_inlet: Point,
void_start_y: i32,
}
#[derive(Debug, Clone)]
enum Wall {
Vertical(VerticalWall),
Horizontal(HorizontalWall),
}
#[derive(Debug, Clone)]
struct VerticalWall {
x: i32,
y1: i32,
y2: i32,
}
#[derive(Debug, Clone)]
struct HorizontalWall {
y: i32,
x1: i32,
x2: i32,
}
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
struct Point {
x: i32,
y: i32,
}
#[derive(Debug, PartialEq, Eq)]
enum DropSandResult {
FellIntoTheVoid,
Settled,
RoomFull,
}
impl Room {
fn parser(input: &str) -> IResult<&str, Self> {
map(
separated_list1(line_ending, separated_list1(tag(" -> "), Point::parser)),
|wall_segments| {
let mut walls = Vec::new();
let mut void_start_y = 0;
for wall_segment in wall_segments {
for point_pair in wall_segment.windows(2) {
walls.push(if point_pair[0].x == point_pair[1].x {
Wall::Vertical(VerticalWall {
x: point_pair[0].x,
y1: point_pair[0].y.min(point_pair[1].y),
y2: point_pair[0].y.max(point_pair[1].y),
})
} else if point_pair[0].y == point_pair[1].y {
Wall::Horizontal(HorizontalWall {
y: point_pair[0].y,
x1: point_pair[0].x.min(point_pair[1].x),
x2: point_pair[0].x.max(point_pair[1].x),
})
} else {
panic!("Invalid wall segment")
});
void_start_y = void_start_y.max(point_pair[0].y);
void_start_y = void_start_y.max(point_pair[1].y);
}
void_start_y =
void_start_y.max(wall_segment.iter().map(|p| p.y).max().unwrap_or(0))
}
Room {
walls,
sand: BTreeSet::new(),
sand_inlet: Point { x: 500, y: 0 },
void_start_y,
}
},
)(input)
}
fn point_is_occupied(&self, p: &Point) -> bool {
p.y >= self.void_start_y + 2
|| self.sand.contains(p)
|| self.walls.iter().any(|w| w.point_is_occupied(p))
}
fn point_is_in_the_void(&self, p: &Point) -> bool {
p.y >= self.void_start_y
}
fn drop_sand(&mut self, allow_infinite_void: bool) -> DropSandResult {
if self.point_is_occupied(&self.sand_inlet) {
return DropSandResult::RoomFull;
}
let mut falling_sand = self.sand_inlet.clone();
loop {
if allow_infinite_void && self.point_is_in_the_void(&falling_sand) {
return DropSandResult::FellIntoTheVoid;
} else if !self.point_is_occupied(&Point {
x: falling_sand.x,
y: falling_sand.y + 1,
}) {
falling_sand.y += 1;
} else if !self.point_is_occupied(&Point {
x: falling_sand.x - 1,
y: falling_sand.y + 1,
}) {
falling_sand.x -= 1;
falling_sand.y += 1;
} else if !self.point_is_occupied(&Point {
x: falling_sand.x + 1,
y: falling_sand.y + 1,
}) {
falling_sand.x += 1;
falling_sand.y += 1;
} else {
self.sand.insert(falling_sand);
return DropSandResult::Settled;
}
}
}
}
impl Wall {
fn point_is_occupied(&self, p: &Point) -> bool {
match self {
Wall::Vertical(VerticalWall { x, y1, y2 }) => p.x == *x && p.y >= *y1 && p.y <= *y2,
Wall::Horizontal(HorizontalWall { y, x1, x2 }) => p.y == *y && p.x >= *x1 && p.x <= *x2,
}
}
}
impl Point {
fn parser(input: &str) -> IResult<&str, Self> {
map(tuple((i32, tag(","), i32)), |(x, _, y)| Point { x, y })(input)
}
}
|
