Setup

.gitignore

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+proof
+
+
+# Added by cargo
+
+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aoc_24"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "aoc_24"
+version = "0.1.0"
+edition = "2021"

src/day1/mod.rs

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+use std::collections::HashSet;
+
+pub struct Day1 {
+    pub input: String,
+}
+
+impl Day1 {
+    pub fn new() -> Day1 {
+        let input = include_bytes!("input");
+        let input = String::from_utf8_lossy(input);
+        Day1 {
+            input: input.to_string(),
+        }
+    }
+
+    pub fn part_one(&self) {
+        let mut left: Vec<i32> = Vec::new();
+        let mut right: Vec<i32> = Vec::new();
+        self.input.lines().for_each(|line| {
+            let mut parts = line.split_whitespace();
+            left.push(parts.next().unwrap().parse().unwrap());
+            right.push(parts.next().unwrap().parse().unwrap());
+        });
+
+        left.sort();
+        right.sort();
+
+        let res = left
+            .iter()
+            .zip(right.iter())
+            .map(|(l, r)| Day1::abs(*l, *r))
+            .sum::<i32>();
+
+        println!("{}", res);
+    }
+
+    fn abs(a: i32, b: i32) -> i32 {
+        if a > b {
+            a - b
+        } else {
+            b - a
+        }
+    }
+
+    pub fn part_two(&self) {
+        let mut left: HashSet<i32> = HashSet::new();
+        let mut right: Vec<i32> = Vec::new();
+        self.input.lines().for_each(|line| {
+            let mut parts = line.split_whitespace();
+            left.insert(parts.next().unwrap().parse().unwrap());
+            right.push(parts.next().unwrap().parse().unwrap());
+        });
+
+        let mut acc = 0;
+        for r in right.iter() {
+            if left.contains(r) {
+                acc = acc + *r;
+            }
+        }
+
+        println!("{}", acc);
+    }
+}

src/main.rs

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+use day1::Day1;
+mod day1;
+
+fn main() {
+    let args = std::env::args().collect::<Vec<String>>();
+    if args.len() != 2 {
+        println!("Usage: {} {{day}}.{{problem}}", args[0]);
+        println!("Example: {} 1.1", args[0]);
+        std::process::exit(1);
+    }
+
+    let problem = args[1].as_str();
+    match problem {
+        "1.1" => Day1::new().part_one(),
+        "1.2" => Day1::new().part_two(),
+        _ => {
+            println!("Bad input: {}", problem);
+            std::process::exit(1);
+        }
+    }
+}