2018 05 (rs)

Author: memark

2018/Cargo.lock

@@ -0,0 +1,12 @@
+[package]
+name = "day-05"
+version = "0.0.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+itertools = "0.10.5"
+
+[dev-dependencies]
+pretty_assertions = "1.3.0"

2018/day-05/Cargo.toml

@@ -0,0 +1,75 @@
+#![allow(unused_imports, dead_code)]
+
+use itertools::Itertools;
+use std::fs;
+
+fn main() {
+    let file = fs::read_to_string("input").unwrap();
+    let file = file.trim();
+
+    let part_1a = react(file).len();
+    println!("{}: {}", stringify!(part_1a), part_1a);
+
+    let part_2a = improve_polymer_and_react(file);
+    println!("{}: {}", stringify!(part_2a), part_2a);
+}
+
+fn improve_polymer_and_react(file: &str) -> usize {
+    ('a'..='z')
+        .map(|c| react(&remove_units(file, c)).len())
+        .min()
+        .unwrap()
+}
+
+fn react(polymer: &str) -> String {
+    let mut result = polymer.to_owned();
+    let mut changed = true;
+    while changed {
+        changed = false;
+        for c in ('a'..='z').chain('A'..='Z') {
+            let from = [c, switch_case(c)].iter().collect::<String>();
+            if result.contains(&from) {
+                result = result.replace(&from, "");
+                changed = true;
+            }
+        }
+    }
+    result
+}
+
+fn remove_units(polymer: &str, c: char) -> String {
+    polymer.replace([c, switch_case(c)], "")
+}
+
+fn switch_case(c: char) -> char {
+    if c.is_ascii_uppercase() {
+        c.to_ascii_lowercase()
+    } else {
+        c.to_ascii_uppercase()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn react_examples() {
+        assert_eq!(react("aA"), "");
+        assert_eq!(react("abBA"), "");
+        assert_eq!(react("abAB"), "abAB");
+        assert_eq!(react("aabAAB"), "aabAAB");
+    }
+
+    #[test]
+    fn react_larger_example() {
+        assert_eq!(react("dabAcCaCBAcCcaDA"), "dabCBAcaDA");
+    }
+
+    #[test]
+    fn part_2_examples() {
+        assert_eq!(remove_units("dabAcCaCBAcCcaDA", 'a'), "dbcCCBcCcD");
+        assert_eq!(react(&remove_units("dabAcCaCBAcCcaDA", 'a')), "dbCBcD");
+    }
+}