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use std::io::{self, Read};
#[derive(Clone, Copy)]
struct Disc {
positions: u32,
position: u32,
}
impl Disc {
fn rotate(&mut self) {
self.position = (self.position + 1) % self.positions;
}
fn is_open(&self) -> bool {
self.position == 0
}
}
impl<'a> From<&'a str> for Disc {
fn from(s: &'a str) -> Disc {
let mut iter = s.trim_right_matches('.').split_whitespace();
Disc {
positions: iter.nth(3).unwrap().parse().unwrap(),
position: iter.last().unwrap().parse().unwrap(),
}
}
}
#[derive(Clone)]
struct Sculpture {
discs: Vec<Disc>,
time: u32,
capsule: usize,
}
impl Sculpture {
fn tick(&mut self) {
self.time += 1;
for disc in &mut self.discs {
disc.rotate()
}
}
fn drop_capsule(&mut self) -> bool {
while self.capsule < self.discs.len() {
self.tick();
if self.discs[self.capsule].is_open() {
self.capsule += 1;
} else {
return false;
}
}
true
}
}
impl<'a> From<&'a str> for Sculpture {
fn from(s: &'a str) -> Sculpture {
Sculpture {
discs: s.lines().map(Disc::from).collect(),
time: 0,
capsule: 0,
}
}
}
fn solve1(input: &str) -> u32 {
let mut sculpture = Sculpture::from(input);
loop {
if sculpture.clone().drop_capsule() {
return sculpture.time;
}
sculpture.tick();
}
}
fn solve2(input: &str) -> u32 {
let mut sculpture = Sculpture::from(input);
sculpture.discs.push(Disc { positions: 11, position: 0 });
loop {
if sculpture.clone().drop_capsule() {
return sculpture.time;
}
sculpture.tick();
}
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve1(&input));
println!("Part 2: {}", solve2(&input));
}
#[test]
fn part1() {
let input = "
Disc #1 has 5 positions; at time=0, it is at position 4.
Disc #2 has 2 positions; at time=0, it is at position 1.
";
assert_eq!(5, solve1(input.trim()));
}
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