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17.rs
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17.rs
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static INPUT_TXT: &str = include_str!("../../input/17.txt");
fn main() {
println!("Part 1: {}", part_1(INPUT_TXT));
println!("Part 2: {}", part_2(INPUT_TXT));
}
type Point = (i64, i64);
#[derive(Debug)]
enum Rock {
Horizontal,
Cross,
Angle,
Vertical,
Square,
}
#[derive(Debug)]
struct Chamber {
grid: Vec<bool>,
height: i64,
rock: Rock,
x: i64,
y: i64,
}
fn to_index((x, y): Point) -> usize {
(y * 7 + x) as usize
}
impl Chamber {
fn new() -> Self {
Self {
grid: vec![false; 7],
height: 1,
rock: Rock::Horizontal,
x: 2,
y: 3,
}
}
fn is_occupied(&self, point: Point) -> bool {
*self.grid.get(to_index(point)).unwrap_or(&false)
}
fn get_points(&self) -> Vec<Point> {
match self.rock {
Rock::Horizontal => (0..4).map(|delta| (self.x + delta, self.y)).collect(),
Rock::Cross => vec![
(self.x, self.y + 1),
(self.x + 1, self.y + 1),
(self.x + 2, self.y + 1),
(self.x + 1, self.y),
(self.x + 1, self.y + 2),
],
Rock::Angle => vec![
(self.x, self.y),
(self.x + 1, self.y),
(self.x + 2, self.y),
(self.x + 2, self.y + 1),
(self.x + 2, self.y + 2),
],
Rock::Vertical => (0..4).map(|delta| (self.x, self.y + delta)).collect(),
Rock::Square => vec![
(self.x, self.y),
(self.x + 1, self.y),
(self.x, self.y + 1),
(self.x + 1, self.y + 1),
],
}
}
fn step(&mut self, direction: char) -> bool {
let points = self.get_points();
self.x += match direction {
'>' if !points
.iter()
.any(|&(x, y)| x == 6 || self.is_occupied((x + 1, y))) =>
{
1
}
'<' if !points
.iter()
.any(|&(x, y)| x == 0 || self.is_occupied((x - 1, y))) =>
{
-1
}
_ => 0,
};
let new_points = self.get_points();
if new_points
.clone()
.into_iter()
.any(|(x, y)| y == 0 || self.is_occupied((x, y - 1)))
{
for (x, y) in new_points {
if y > self.height - 1 {
self.height = y + 1;
self.grid.extend(vec![
false;
(self.height as usize + 1 - self.grid.len() / 7) * 7
]);
}
self.grid[to_index((x, y))] = true;
}
self.rock = match self.rock {
Rock::Horizontal => Rock::Cross,
Rock::Cross => Rock::Angle,
Rock::Angle => Rock::Vertical,
Rock::Vertical => Rock::Square,
Rock::Square => Rock::Horizontal,
};
self.y = self.height + 3;
self.x = 2;
true
} else {
self.y -= 1;
false
}
}
}
fn part_1(input: &str) -> i64 {
let mut ops = input.trim().chars().cycle();
let mut chamber = Chamber::new();
let mut count: usize = 0;
loop {
if count == 2022 {
break chamber.height;
}
if chamber.step(ops.next().unwrap()) {
count += 1;
}
}
}
fn part_2(input: &str) -> i64 {
let mut ops = input.trim().chars().cycle();
let mut chamber = Chamber::new();
let deltas = {
let mut deltas = [0; 5000];
let mut previous = 0;
let mut count = 0;
loop {
if count == 5000 {
break deltas;
}
if chamber.step(ops.next().unwrap()) {
deltas[count] = chamber.height - previous;
previous = chamber.height;
count += 1;
}
}
};
let (offset, size) = (0..500)
.find_map(|offset| {
let delta_iter = deltas.iter().skip(offset);
let size = (2..=2500).find(|size| {
let window = deltas[offset..offset + size].iter().cycle();
delta_iter.clone().zip(window).all(|(a, b)| a == b)
});
size.map(|size| (offset, size))
})
.unwrap();
let mut delta_iter = deltas.iter();
let mut count = 1_000_000_000_000;
let offset_delta = delta_iter.by_ref().take(offset).sum::<i64>();
count -= offset;
let cycle_deltas: Vec<_> = delta_iter.take(size).copied().collect();
let cycle_delta = cycle_deltas.iter().sum::<i64>();
let cycle_count = (count / size) as i64;
count %= size;
offset_delta + cycle_count * cycle_delta + cycle_deltas.into_iter().take(count).sum::<i64>()
}
#[cfg(test)]
mod day_17_tests {
use super::*;
static INPUT: &str = ">>><<><>><<<>><>>><<<>>><<<><<<>><>><<>>";
#[test]
fn test_part_1() {
assert_eq!(part_1(INPUT), 3068);
assert_eq!(part_1(INPUT_TXT), 3186);
}
#[test]
fn test_part_2() {
assert_eq!(part_2(INPUT), 1_514_285_714_288);
assert_eq!(part_2(INPUT_TXT), 1_566_376_811_584);
}
}