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fn adjescent(p: &(usize,usize,usize), mx:usize) -> Vec<(usize,usize,usize)> {
let mut v = vec![];
if p.0+1 < mx {
v.push((p.0+1,p.1,p.2));
}
if p.1+1 < mx {
v.push((p.0,p.1+1,p.2));
}
if p.2+1 < mx {
v.push((p.0,p.1,p.2+1));
}
if p.0 > 0 {
v.push((p.0-1,p.1,p.2));
}
if p.1 > 0 {
v.push((p.0,p.1-1,p.2));
}
if p.2 > 0 {
v.push((p.0,p.1,p.2-1));
}
v
}
#[derive(Debug,PartialEq)]
enum State {Rock,Unknown,OutsideAir}
fn mark_outside(grid: &mut Vec<Vec<Vec<State>>>, curr: &(usize,usize,usize), mx: usize) {
for cell in adjescent(curr, mx) {
if let State::Unknown = grid[cell.0][cell.1][cell.2] {
grid[cell.0][cell.1][cell.2] = State::OutsideAir;
mark_outside(grid, &cell, mx);
}
}
}
fn surface_area(grid: &Vec<Vec<Vec<State>>>, cubes: &Vec<(usize,usize,usize)>, mx: usize) -> usize {
let surface_area: usize = cubes.iter().map(|cube| {
let mut score = 6;
for p in adjescent(cube, mx) {
if let State::Rock = grid[p.0][p.1][p.2] {
score -= 1;
}
}
score
}).sum();
surface_area
}
pub fn run(input:String) {
let cubes = input.lines()
.map(|line| {
let res = line.split(",").map(|t| {t.parse::<usize>().unwrap()}).collect::<Vec<usize>>();
if res.len() != 3 {
panic!("malformatted line! {}", line);
}
(res[0], res[1], res[2])
}).collect::<Vec<(usize,usize,usize)>>();
let mx: usize = cubes.iter().map(|t| {vec![t.0, t.1, t.2]}).flatten().max().unwrap() + 3;
// Allocate a 3d space, and mark the rocky cubes
let mut grid: Vec<Vec<Vec<State>>> = (0..mx).map(|_| {(0..mx).map(|_| {(0..mx).map(|_| {State::Unknown}).collect()}).collect()}).collect();
for cube in cubes.iter() {
grid[cube.0][cube.1][cube.2] = State::Rock;
}
// Now count cubes. Each contributes 6, minus number of adjescent rocky cubes
println!("Day 18 pt1: {}", surface_area(&grid, &cubes, mx));
// So... how can I remove pockets of air to get the _outside_ surface area?
// ans; fill in the inside areas!
// pick a spot definitely on the outside;; iterate out until all the outside is marked.
// Anything remaining is pockets, fill it in, re-calculate the outside surface area.
grid[0][0][0] = State::OutsideAir;
mark_outside(&mut grid, &(0,0,0), mx);
// All remaining Unknown cells are air pockets, fill 'em in
for x in 0..mx {
for y in 0..mx {
for z in 0..mx {
match grid[x][y][z] {
State::Unknown => {
grid[x][y][z] = State::Rock;
},
_ => ()
};
}
}
}
// recalculate the surface area
println!("Day 18 pt2: {}", surface_area(&grid, &cubes, mx));
}
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