Year 2018: Day 05

CHANGELOG.md

@@ -10,6 +10,10 @@ Of note:
 - The changelog 2015.5.2 has been rewritten from each commit content.
 - This file may be amended entirely in the future to adhere to the [GNU Changelog style](https://www.gnu.org/prep/standards/html_node/Style-of-Change-Logs.html#Style-of-Change-Logs)
 
+## [2018.5.1]
+### Added
+- Solved [exercice for 2018, day 05](src/year_2018/05.rs).
+
 ## [2018.4.1]
 ### Added
 - Solved [exercice for 2018, day 04](src/year_2018/04.rs).

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "advent-rs"
-version = "2018.4.1"
+version = "2018.5.1"
 edition = "2021"
 authors = ["Arnaud 'red' Rouyer"]
 readme = "README.md"

NOTES_2018.md

@@ -14,3 +14,7 @@ Not much we haven't seen last year.
 ## Day 04: Repose Record
 
 There's something about this "find the most used record" type of exercises that I dislike.
+
+## Day 05: Alchemical Reduction
+
+As a programmer, your MUST have used, at least once, the command [`man ascii`](https://man.archlinux.org/man/core/man-pages/ascii.7.en), if only to find the integer value of a specific number. But were you to look specifically at the hexadecimal table, something may have caught your attention: uppercase letters, and their equivalent lowercase values, are all separated by 32 characters. Now, isn't that a nice number that plays VERY WELL with bit masks? Here's a little [playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=d9a88346debfc3c2470c6b1527202f30) to help you!

README.md

@@ -8,7 +8,7 @@ I'm also adding notes that may be useful if you're (like me) discovering Rust:
 - [2015, complete!](NOTES_2015.md)
 - [2016, complete!](NOTES_2016.md)
 - [2017, complete!](NOTES_2017.md)
-- [2018, up to day 04](NOTES_2018.md)
+- [2018, up to day 05](NOTES_2018.md)
 
 # Regarding style rules
 I'm gonna use a mix of what `cargo fmt` does, with some stuff that feels more natural to me.

benches/year_2018.rs

@@ -2,6 +2,7 @@ use advent_rs::year_2018::day_01;
 use advent_rs::year_2018::day_02;
 use advent_rs::year_2018::day_03;
 use advent_rs::year_2018::day_04;
+use advent_rs::year_2018::day_05;
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 
 fn year_2018_day_01(c: &mut Criterion) {
@@ -64,11 +65,27 @@ fn year_2018_day_04(c: &mut Criterion) {
   g2018_day_04.finish();
 }
 
+fn year_2018_day_05(c: &mut Criterion) {
+  let input = include_str!("../inputs/year_2018/day_05_input");
+  assert_eq!(day_05::day_05_v1(input), 11_298);
+  assert_eq!(day_05::day_05_v2(input), 5_148);
+
+  let mut g2018_day_05 = c.benchmark_group("year_2018::day_05");
+  g2018_day_05.bench_function("year_2018::day_05_v1", |b| {
+    b.iter(|| day_05::day_05_v1(black_box(input)))
+  });
+  g2018_day_05.bench_function("year_2018::day_05_v2", |b| {
+    b.iter(|| day_05::day_05_v2(black_box(input)))
+  });
+  g2018_day_05.finish();
+}
+
 criterion_group!(
   benches,
   year_2018_day_01,
   year_2018_day_02,
   year_2018_day_03,
-  year_2018_day_04
+  year_2018_day_04,
+  year_2018_day_05
 );
 criterion_main!(benches);

src/year_2018.rs

@@ -6,6 +6,7 @@ pub mod day_01;
 pub mod day_02;
 pub mod day_03;
 pub mod day_04;
+pub mod day_05;
 
 pub fn solve(day: u8, part: u8, input: impl Into<String>) -> Option<String> {
   if part > 2 {
@@ -17,6 +18,7 @@ pub fn solve(day: u8, part: u8, input: impl Into<String>) -> Option<String> {
     2 => Some(day_02::day_02(part, input).to_string()),
     3 => Some(day_03::day_03(part, input).to_string()),
     4 => Some(day_04::day_04(part, input).to_string()),
+    5 => Some(day_05::day_05(part, input).to_string()),
     _ => None,
   }
 }
@@ -52,4 +54,11 @@ mod tests {
     assert_eq!(day_04::day_04_v1(input), 35_623);
     assert_eq!(day_04::day_04_v2(input), 23_037);
   }
+
+  #[test]
+  fn day_05() {
+    let input = include_str!("../inputs/year_2018/day_05_input");
+    assert_eq!(day_05::day_05_v1(input), 11_298);
+    assert_eq!(day_05::day_05_v2(input), 5_148);
+  }
 }

src/year_2018/day_05.rs

@@ -0,0 +1,55 @@
+fn react_polymer(input: &str) -> u16 {
+  input
+    .bytes()
+    .fold(vec![], |mut acc, chr| {
+      if !acc.is_empty() && *acc.last().unwrap() == (chr ^ 32) {
+        acc.pop();
+      } else {
+        acc.push(chr);
+      }
+      acc
+    })
+    .len() as u16
+}
+
+pub fn day_05_v1(input: impl Into<String>) -> u16 {
+  react_polymer(&input.into())
+}
+
+pub fn day_05_v2(input: impl Into<String>) -> u16 {
+  let input = input.into();
+  let maj = 'A'..='Z';
+  ('a'..='z')
+    .zip(maj)
+    .map(|(min, maj)| react_polymer(&input.replace([min, maj], "")))
+    .min()
+    .unwrap()
+}
+
+solvable!(day_05, day_05_v1, day_05_v2, u16);
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  const SAMPLE: &str = "dabAcCaCBAcCcaDA";
+
+  #[test]
+  fn works_with_samples_v1() {
+    let sample_one = [
+      ("aA", 0),
+      ("abBA", 0),
+      ("abAB", 4),
+      ("aabAAB", 6),
+      (SAMPLE, 10),
+    ];
+    for (sample, result) in sample_one {
+      assert_eq!(day_05_v1(sample), result);
+    }
+  }
+
+  #[test]
+  fn works_with_samples_v2() {
+    assert_eq!(day_05_v2(SAMPLE), 4);
+  }
+}