160 lines
4.1 KiB
Rust
160 lines
4.1 KiB
Rust
#![feature(test)]
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use std::cmp::Ordering;
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use anyhow::Result;
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use aoc::Solver;
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// -- Runners --
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fn main() -> Result<()> {
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Day::solve()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn part1_test1() -> Result<()> {
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Day::test(Day::part1, "test-1", 1320)
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}
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#[test]
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fn part1_solution() -> Result<()> {
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Day::test(Day::part1, "input", 511416)
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}
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#[test]
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fn part2_test1() -> Result<()> {
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Day::test(Day::part2, "test-1", 145)
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}
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#[test]
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fn part2_solution() -> Result<()> {
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Day::test(Day::part2, "input", 290779)
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}
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// Benchmarks
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extern crate test;
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#[bench]
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#[ignore]
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fn part1_bench(b: &mut test::Bencher) {
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Day::benchmark(Day::part1, b)
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}
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#[bench]
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#[ignore]
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fn part2_bench(b: &mut test::Bencher) {
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Day::benchmark(Day::part2, b)
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}
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}
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#[derive(Debug, Clone, PartialEq, Eq)]
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enum Action<'a> {
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Add { label: &'a str, focal_length: usize },
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Remove { label: &'a str },
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}
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impl<'a> Action<'a> {
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fn index(&self) -> usize {
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match self {
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Action::Add { label, .. } | Action::Remove { label } => label
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.chars()
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.map(|c| c as usize)
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.fold(0, |acc, num| ((acc + num) * 17) % 256),
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}
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}
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}
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// -- Solution --
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pub struct Day;
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impl aoc::Solver for Day {
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type Output1 = usize;
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type Output2 = usize;
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fn day() -> u8 {
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15
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}
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fn part1(input: &str) -> Self::Output1 {
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input
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.trim()
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.split(',')
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.map(|sequence| {
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sequence
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.chars()
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.map(|c| c as usize)
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.fold(0, |acc, num| ((acc + num) * 17) % 256)
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})
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.sum()
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}
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fn part2(input: &str) -> Self::Output2 {
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let actions: Vec<_> = input
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.trim()
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.split(',')
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.map(|sequence| {
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if sequence.ends_with('-') {
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let label = sequence.split_once('-').unwrap().0;
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Action::Remove { label }
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} else {
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let (label, focal_length) = sequence.split_once('=').unwrap();
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let focal_length = focal_length.parse().unwrap();
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Action::Add {
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label,
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focal_length,
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}
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}
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})
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.collect();
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let mut boxes: [Vec<(&str, usize)>; 256] = std::array::from_fn(|_| Vec::new());
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for action in &actions {
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let index = action.index();
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match action {
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Action::Add {
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label,
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focal_length,
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} => {
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// NOTE: Using a library like OrderedMap would make this trivially easy
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if let Some(position) = boxes[index]
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.iter()
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.position(|lens| lens.0.cmp(label) == Ordering::Equal)
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{
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// If a lens with this label is already in the box, replace it
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boxes[index][position].1 = *focal_length;
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} else {
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// Otherwise add it to the end of the box
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boxes[index].push((label, *focal_length));
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}
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}
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Action::Remove { label } => {
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if let Some(position) = boxes[index]
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.iter()
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.position(|lens| lens.0.cmp(label) == Ordering::Equal)
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{
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// A lens with the label exists, remove it
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boxes[index].remove(position);
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}
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}
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}
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}
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boxes
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.iter()
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.enumerate()
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.map(|(index, b)| {
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b.iter()
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.enumerate()
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.map(|(position, (_, focal_length))| {
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(1 + index) * (1 + position) * focal_length
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})
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.sum::<usize>()
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})
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.sum()
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}
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}
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