Day 1, 2 and 3

day3/src/main.rs

@@ -0,0 +1,47 @@
+use std::{collections::HashSet, fs::read_to_string};
+
+use color_eyre::{eyre::*, Result};
+use itertools::Itertools;
+
+fn priority(item: &char) -> usize {
+    ('a'..='z')
+        .position(|c| *item == c)
+        .map(|i| i + 1)
+        .or_else(|| ('A'..='Z').position(|c| *item == c).map(|i| i + 27))
+        .unwrap_or(0)
+}
+
+fn initial(input: &str) -> (usize, usize) {
+    let output1 = input
+        .lines()
+        .map(|line| {
+            let (compartment1, compartment2) = line.split_at(line.len() / 2);
+            let compartment1 = compartment1.chars().collect::<HashSet<_>>();
+            let compartment2 = compartment2.chars().collect::<HashSet<_>>();
+            compartment1
+                .intersection(&compartment2)
+                .map(priority)
+                .sum::<usize>()
+        })
+        .sum();
+    let output2 = input
+        .lines()
+        .chunks(3)
+        .into_iter()
+        .map(|group| {
+            group
+                .map(|line| line.chars().collect::<HashSet<_>>())
+                .coalesce(|a, b| Ok(a.intersection(&b).copied().collect()))
+                .map(|set| set.iter().map(priority).sum::<usize>())
+                .sum::<usize>()
+        })
+        .sum();
+    (output1, output2)
+}
+
+fn main() -> Result<()> {
+    let input = read_to_string("input.txt").wrap_err("reading input.txt")?;
+    let output = initial(&input);
+    println!("output: {output:?}");
+    Ok(())
+}