Add day03, 2022

2 files changed, 112 insertions, 0 deletions

diff --git a/2022/rust/day03/Cargo.toml b/2022/rust/day03/Cargo.toml
new file mode 100644
index 0000000..115d7fa
--- /dev/null
+++ b/2022/rust/day03/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "day03"
+version = "0.1.0"
+authors = ["cos <cos>"]
+edition = "2021"
+
+[dependencies]
+aoc = { path = "../../../common/rust/aoc" }
+anyhow = "1.0"
diff --git a/2022/rust/day03/src/main.rs b/2022/rust/day03/src/main.rs
new file mode 100644
index 0000000..a3e4fb3
--- /dev/null
+++ b/2022/rust/day03/src/main.rs
@@ -0,0 +1,103 @@
+use {
+    anyhow::{
+        anyhow,
+        Context,
+        Result,
+    },
+    std::{
+        env::args,
+        fs::File,
+        io::{
+            BufRead,
+            BufReader,
+        },
+        path::Path,
+    },
+};
+
+fn item_priority(item: char) -> Option<usize> {
+    match item {
+        'a'..='z' => Some((item as u32 - 'a' as u32 + 1) as usize),
+        'A'..='Z' => Some((item as u32 - 'A' as u32 + 27) as usize),
+        _ => None,
+    }
+}
+
+#[derive(Debug)]
+struct Rucksack {
+    compartments: Vec<String>,
+}
+
+impl Rucksack {
+    fn new(items: &str) -> Self {
+        let (first, second) = items.split_at(items.len()/2);
+        let compartments = vec![String::from(first), String::from(second)];
+        Self {
+            compartments,
+        }
+    }
+
+    fn contains(&self, needle: char) -> bool {
+        self.compartments[0].contains(needle) || self.compartments[1].contains(needle)
+    }
+
+    fn common_items(&self) -> String {
+        self.compartments[0].chars().filter(|item| self.compartments[1].contains(*item)).collect()
+    }
+
+    fn find_badge(&self, other: &Rucksack) -> String {
+        self.compartments[0].chars().chain(self.compartments[1].chars()).filter(|item|
+            other.contains(*item)).collect()
+    }
+}
+
+fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<Rucksack>> {
+    let reader = BufReader::new(File::open(filename)?);
+
+    reader.lines().map(
+        |v| {
+            let s = v?;
+            Ok(Rucksack::new(&s))
+        }
+    ).collect()
+}
+
+fn part1(input: &[Rucksack]) -> Result<usize> {
+    Ok(input.iter().filter_map(|rucksack| {
+        if let Some(item) = rucksack.common_items().chars().next() {
+            item_priority(item)
+        } else {
+            None
+        }
+    }).sum())
+}
+
+fn part2(input: &[Rucksack]) -> Result<usize> {
+    Ok(input.chunks(3).filter_map(|rucksacks| {
+        let some_candidates = rucksacks[0].find_badge(&rucksacks[1]);
+        let other_candidates = rucksacks[0].find_badge(&rucksacks[2]);
+        let common: String = some_candidates.chars().filter(|item|
+            other_candidates.contains(*item)).collect();
+        if let Some(item) = common.chars().next() {
+            item_priority(item)
+        } else {
+            None
+        }
+    }).sum())
+}
+
+fn main() -> Result<()> {
+    let ( do_part_1, do_part_2 ) = aoc::do_parts();
+
+    let filename = args().nth(1).ok_or_else(|| anyhow!("Missing input filename"))?;
+    let input = read_input(filename).context("Could not read input")?;
+    if do_part_1 {
+        let solution = part1(&input).context("No solution for part 1")?;
+        println!("Part1, solution found to be: {}", solution);
+    }
+    if do_part_2 {
+        let solution = part2(&input).context("No solution for part 2")?;
+        println!("Part2, solution found to be: {}", solution);
+    }
+    Ok(())
+}