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|
use std::collections::HashMap;
static DAY: u8 = 14;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", sand_before_abyss(&input));
println!("{DAY}b: {}", sand_to_rest(&input));
}
#[derive(Debug)]
enum Material {
Rock,
Sand,
}
fn parse_map(input: &[String]) -> HashMap<(isize,isize),Material> {
let mut map = HashMap::new();
for line in input {
let mut path = Vec::new();
for coord in line.split(" -> ") {
let (x,y) = coord.split_once(',').expect("coordinate needs to contain ,");
let x = x.parse::<isize>().expect("x coord should be number");
let y = y.parse::<isize>().expect("y coord should be number");
path.push((x,y));
}
for pos in path.windows(2) {
let (x1, x2) = if pos[0].0 < pos[1].0 {
(pos[0].0, pos[1].0)
} else {
(pos[1].0, pos[0].0)
};
let (y1, y2) = if pos[0].1 < pos[1].1 {
(pos[0].1, pos[1].1)
} else {
(pos[1].1, pos[0].1)
};
for x in x1 ..= x2 {
for y in y1 ..= y2 {
map.insert((x,y), Material::Rock);
}
}
}
}
map
}
fn next_sand_pos(map: &mut HashMap<(isize,isize),Material>, pos: (isize,isize)) -> Option<(isize,isize)> {
let next_positions = [
(pos.0, pos.1 + 1),
(pos.0 - 1, pos.1 + 1),
(pos.0 + 1, pos.1 + 1),
];
next_positions.iter().find(|next_pos| !map.contains_key(next_pos)).copied()
}
fn sand_above_abyss(map: &mut HashMap<(isize,isize),Material>, above: isize) -> bool {
let mut pos = (500,0);
while pos.1 <= above {
match next_sand_pos(map, pos) {
Some(next_pos) => pos = next_pos,
None => {
map.insert(pos, Material::Sand);
break;
}
}
}
pos.1 <= above
}
fn sand_at_source(map: &mut HashMap<(isize,isize),Material>, floor: isize) -> bool {
let mut pos = (500,0);
loop {
match next_sand_pos(map, pos) {
Some(next_pos) => {
if next_pos.1 == floor {
map.insert(pos, Material::Sand);
break;
}
pos = next_pos;
},
None => {
map.insert(pos, Material::Sand);
break;
}
}
}
pos == (500,0)
}
fn sand_before_abyss(input: &[String]) -> usize {
let mut map = parse_map(input);
let lowest_rock = *map.keys().max_by_key(|(_,y)| y).expect("map should have a rock");
let mut sand = 0;
while sand_above_abyss(&mut map, lowest_rock.1) {
sand += 1;
}
sand
}
fn sand_to_rest(input: &[String]) -> usize {
let mut map = parse_map(input);
let floor = map.keys().max_by_key(|(_,y)| y).expect("map should have a rock").1 + 2;
let mut sand = 0;
while !sand_at_source(&mut map, floor) {
sand += 1;
}
sand + 1
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"498,4 -> 498,6 -> 496,6",
"503,4 -> 502,4 -> 502,9 -> 494,9",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(sand_before_abyss(&input), 24);
assert_eq!(sand_to_rest(&input), 93);
}
}
|
