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25
11/Cargo.lock generated
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@ -1,25 +0,0 @@
# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
version = 3
[[package]]
name = "day11"
version = "0.1.0"
dependencies = [
"itertools",
]
[[package]]
name = "either"
version = "1.13.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
[[package]]
name = "itertools"
version = "0.13.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
dependencies = [
"either",
]

7
11/Cargo.toml
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@ -1,7 +0,0 @@
[package]
name = "day11"
version = "0.1.0"
edition = "2021"
[dependencies]
itertools = "0.13.0"

132
11/src/main.rs
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@ -1,132 +0,0 @@
use std::collections::HashMap;
use std::fs::File;
use std::io::{BufRead, BufReader, Lines};
use std::time::{Duration, Instant};
use itertools::Itertools;
// BOILERPLATE
type InputIter = Lines<BufReader<File>>;
pub fn get_input() -> InputIter {
let f = File::open("input").unwrap();
let br = BufReader::new(f);
br.lines()
}
fn duration_format(duration: Duration) -> String {
match duration.as_secs_f64() {
x if x > 1.0 => format!("{:.3}s", x),
x if x > 0.010 => format!("{:.3}ms", x * 1e3),
x => format!("{:.3}us", x * 1e6),
}
}
fn main() {
let input = get_input();
let start = Instant::now();
let ans1 = problem1(input);
let duration1 = start.elapsed();
println!("Problem 1 solution: {} [{}]", ans1, duration_format(duration1));
let input = get_input();
let start = Instant::now();
let ans2 = problem2(input);
let duration2 = start.elapsed();
println!("Problem 2 solution: {} [{}]", ans2, duration_format(duration2));
println!("Total duration: {}", duration_format(duration1 + duration2));
}
#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
struct Stone {
value: u64,
}
impl Stone {
fn blink_once(self) -> Vec<Stone> {
let n_digits = if self.value == 0 { 1 } else { self.value.ilog10() + 1 };
if self.value == 0 {
vec![Stone { value: 1 }]
} else if n_digits % 2 == 0 {
let parts = (
self.value / 10u64.pow(n_digits / 2),
self.value % 10u64.pow(n_digits / 2),
);
vec![Stone { value: parts.0 }, Stone { value: parts.1 }]
} else {
vec![Stone {
value: self.value * 2024,
}]
}
}
fn blink(self, times: usize) -> Vec<Stone> {
let mut stones = vec![self];
for _ in 0..times {
stones = stones.iter().flat_map(|stone| stone.blink_once()).collect();
}
stones
}
}
// PROBLEM 1 solution
fn problem1<T: BufRead>(mut input: Lines<T>) -> u64 {
let stones = input
.next()
.unwrap()
.unwrap()
.split_ascii_whitespace()
.map(|v| Stone {
value: v.parse().unwrap(),
})
.collect_vec();
stones.iter().flat_map(|stone| stone.blink(25)).count() as u64
}
fn count_blinks(stone: Stone, blinks: u64, cache: &mut HashMap<(u64, Stone), u64>) -> u64 {
if cache.contains_key(&(blinks, stone)) {
return cache[&(blinks, stone)];
}
let stones = stone.blink_once();
let result = if blinks == 1 {
stones.len() as u64
} else {
stones.iter().map(|s| count_blinks(*s, blinks - 1, cache)).sum()
};
cache.insert((blinks, stone), result);
result
}
// PROBLEM 2 solution
fn problem2<T: BufRead>(mut input: Lines<T>) -> u64 {
let stones = input
.next()
.unwrap()
.unwrap()
.split_ascii_whitespace()
.map(|v| Stone {
value: v.parse().unwrap(),
})
.collect_vec();
let mut cache = HashMap::new();
stones.iter().map(|s| count_blinks(*s, 75, &mut cache)).sum()
}
#[cfg(test)]
mod tests {
use crate::*;
use std::io::Cursor;
const EXAMPLE: &str = &"125 17";
#[test]
fn problem1_example() {
let c = Cursor::new(EXAMPLE);
assert_eq!(problem1(c.lines()), 55312);
}
#[test]
fn problem2_example() {
let c = Cursor::new(EXAMPLE);
assert_eq!(problem2(c.lines()), 55312);
}
}