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|
static DAY: u8 = 11;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", blink_stones(&input[0]));
println!("{DAY}b: {}", 0);
}
enum Stone {
Number(u64),
Split(Box<Stone>,Box<Stone>),
}
impl Stone {
fn blink_number(number: u64) -> Stone {
/* rule 1 */
if number == 0 {
return Stone::Number(1);
}
/* rule 2 */
let number_str = number.to_string();
if number_str.len() % 2 == 0 {
let left = number_str.chars().take(number_str.len() / 2).collect::<String>();
let right = number_str.chars().skip(number_str.len() / 2).collect::<String>();
let left = left.parse::<u64>().unwrap();
let right = right.parse::<u64>().unwrap();
return Stone::Split(Box::new(Stone::Number(left)), Box::new(Stone::Number(right)));
}
/* rule 3 */
Stone::Number(2024 * number)
}
fn blink_stone(stone: &Stone) -> Stone {
match stone {
Stone::Number(number) => Self::blink_number(*number),
Stone::Split(left, right) => Stone::Split(Box::new(Self::blink_stone(left)), Box::new(Self::blink_stone(right))),
}
}
fn blink(&mut self) {
*self = Self::blink_stone(self);
}
fn count(&self) -> usize {
match self {
Stone::Number(_) => 1,
Stone::Split(left, right) => left.count() + right.count(),
}
}
}
fn blink_stones(input: &str) -> usize {
let mut stones = Vec::new();
for val in input.split(" ") {
let number = val.parse::<u64>().unwrap();
stones.push(Stone::Number(number));
}
for _ in 0..25 {
for stone in stones.iter_mut() {
stone.blink();
}
}
stones.iter()
.map(|stone| stone.count())
.sum()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = "125 17";
assert_eq!(blink_stones(input), 55312);
}
}
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