day 3

2022/Cargo.toml

@@ -15,6 +15,10 @@ path = "src/day1.rs"
 name = "day2"
 path = "src/day2.rs"
 
+[[bin]]
+name = "day3"
+path = "src/day3.rs"
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]

2022/src/day3.rs

@@ -0,0 +1,103 @@
+use std::str::FromStr;
+
+
+const DATA: &'static str = include_str!("../data/day3.txt");
+// const DATA: &'static str = "
+// vJrwpWtwJgWrhcsFMMfFFhFp
+// jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+// PmmdzqPrVvPwwTWBwg
+// wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+// ttgJtRGJQctTZtZT
+// CrZsJsPPZsGzwwsLwLmpwMDw
+// ";
+
+
+#[derive(Debug)]
+enum DataError {
+    Imbalanced,
+    UnknownValue,
+    NoDuplicate,
+    NoTriplicate,
+    ShortGroup,
+}
+
+
+struct Rucksack {
+    left: Vec<u8>,
+    right: Vec<u8>,
+}
+
+impl Rucksack {
+    fn find_duplicate(&self) -> Option<u8> {
+        // pretty sure this is faster than hash set, given the sizes involved
+        self.left.iter()
+            .find(|c| self.right.contains(c))
+            .map(|c| *c)
+    }
+
+    fn iter_all(&self) -> impl Iterator<Item = &u8> {
+        self.left.iter().chain(self.right.iter())
+    }
+
+    fn contains(&self, v: u8) -> bool {
+        self.left.contains(&v) || self.right.contains(&v)
+    }
+}
+
+impl FromStr for Rucksack {
+    type Err = DataError;
+
+    fn from_str(line: &str) -> Result<Rucksack, DataError> {
+        let line = line.trim();
+        if line.len() % 2 != 0 {
+            return Err(DataError::Imbalanced);
+        }
+        let (a, b) = line.as_bytes().split_at(line.len() / 2);
+        Ok(Rucksack {
+            left: a.into(),
+            right: b.into(),
+        })
+    }
+}
+
+
+fn priority(c: u8) -> Result<u64, DataError> {
+    match c {
+        // lowercase
+        97..=122 => Ok(c as u64 - 96),
+        // uppercase
+        65..=90 => Ok(c as u64 - 38),
+        _ => Err(DataError::UnknownValue),
+    }
+}
+
+
+fn main() -> Result<(), DataError> {
+    let mut dup_total = 0;
+    let rucks = DATA.trim()
+        .split("\n")
+        .map(|line| Rucksack::from_str(line))
+        .collect::<Result<Vec<Rucksack>, DataError>>()?;
+
+    for ruck in rucks.iter() {
+        let dup = ruck.find_duplicate()
+            .ok_or(DataError::NoDuplicate)?;
+        dup_total += priority(dup)?;
+    }
+    println!("Part 1: {dup_total}");
+
+    let mut groups_total = 0;
+    for (idx, ruck) in rucks.iter().enumerate().step_by(3) {
+        if idx > rucks.len() - 3 {
+            return Err(DataError::ShortGroup);
+        }
+
+        let badge = *ruck.iter_all()
+            .find(|&v| rucks[idx + 1].contains(*v) && rucks[idx + 2].contains(*v))
+            .ok_or(DataError::NoTriplicate)?;
+        groups_total += priority(badge)?;
+    }
+    println!("Part 2: {groups_total}");
+
+    Ok(())
+}

2022/src/lib.rs

@@ -1,12 +0,0 @@
-#[allow(unused_macros)]
-macro_rules! get_data {
-    ($filename: literal) => {
-        include_str!(concat!("../data/", $filename, ".txt"))
-    }
-}
-
-
-#[allow(dead_code)]
-fn main() {
-    todo!();
-}