Day 3 solution, plus some mucking about with the template code.

2022/src/day03.rs

@@ -0,0 +1,53 @@
+use std::io;
+use std::vec::Vec;
+use std::collections::HashSet;
+
+use crate::utils;
+
+pub fn execute() -> Result<(), io::Error> {
+    let mut score = 0;
+    let mut sacks: Vec<HashSet<u8>> = Vec::new();
+
+    for line in utils::read_lines("input/day03.txt")? {
+        let text = line?;
+        let (text1, text2) = text.split_at(text.len() / 2);
+        let mut pouch1 = HashSet::new();
+        let mut pouch2 = HashSet::new();
+        for i in 0..text1.len() {
+            pouch1.insert(text1.as_bytes()[i]);
+            pouch2.insert(text2.as_bytes()[i]);
+        }
+
+        let intersect: HashSet<_> = pouch1.intersection(&pouch2).cloned().collect();
+        score += get_score(&intersect);
+
+        sacks.push(pouch1.union(&pouch2).cloned().collect());
+    }
+
+    let mut score2 = 0;
+    for group in sacks.chunks(3) {
+        let mut intersect: HashSet<u8> = group[0].intersection(&group[1]).cloned().collect();
+        intersect = intersect.intersection(&group[2]).cloned().collect();
+        score2 += get_score(&intersect);
+    }
+    
+    utils::print_step(1, score as u64);
+    utils::print_step(2, score2 as u64);
+    Ok(())
+}
+
+fn get_score(intersect: &HashSet<u8>) -> u32 {
+    if intersect.len() > 1 {
+        panic!("More than one overlapping item.");
+    }
+
+    if let Some(item) = intersect.iter().next() {
+        if *item > 0x60 {
+            return (*item - 0x60) as u32;
+        }
+
+        return ((*item - 0x40) + 26) as u32;
+    }
+
+    panic!("No items in intersection.");
+}

2022/src/main.rs

@@ -1,11 +1,12 @@
 use std::env;
 use std::io;
+mod utils;
 
-const LATEST: u8 = 2;
+const LATEST: u8 = 3;
 
 mod day01;
 mod day02;
-// mod day03;
+mod day03;
 // mod day04;
 // mod day05;
 // mod day06;
@@ -34,7 +35,7 @@ fn main() -> io::Result<()> {
     match day {
         1 => day01::execute(),
         2 => day02::execute(),
-        // 3 => day03::execute(),
+        3 => day03::execute(),
         // 4 => day04::execute(),
         // 5 => day05::execute(),
         // 6 => day06::execute(),

2022/src/template.rs

@@ -1,6 +1,11 @@
-mod utils;
+use std::io;
+
+use crate::utils;
 
 pub fn execute() -> Result<(), io::Error> {
+    for line in utils::read_lines("input/day03.txt")? {
+        let text = line?;
+    }
 
     Ok(())
 }

2022/src/utils.rs

@@ -2,11 +2,11 @@ use std::io;
 use std::io::prelude::*;
 use std::fs::File;
 
-fn read_lines(filename: &str) -> io::Result<impl Iterator<Item = io::Result<String>>> {
+pub fn read_lines(filename: &str) -> io::Result<impl Iterator<Item = io::Result<String>>> {
     let file = File::open(filename)?;
     Ok(io::BufReader::new(file).lines())
 }
 
-fn print_step(step: i8, value: u64) {
-    println!("Step {step} solution: {solution}");
+pub fn print_step(step: i8, value: u64) {
+    println!("Step {step} solution: {value}");
 }