Day 1

4 files changed, 55 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..5d41a28
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "aoc2024"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..3453c1c
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "aoc2024"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/src/bin/1.rs b/src/bin/1.rs
new file mode 100644
index 0000000..df5dead
--- /dev/null
+++ b/src/bin/1.rs
@@ -0,0 +1,41 @@
+use std::{
+    collections::HashMap,
+    error::Error,
+    fs::File,
+    io::{BufRead, BufReader},
+};
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let f = File::open("input/1")?;
+    let f = BufReader::new(f);
+    let mut list_a: Vec<i64> = Vec::new();
+    let mut list_b: Vec<i64> = Vec::new();
+    for line in f.lines() {
+        let line = line?;
+        let (a, b) = line.trim_end().split_once("   ").ok_or("Invalid line")?;
+        list_a.push(a.parse()?);
+        list_b.push(b.parse()?);
+    }
+    list_a.sort();
+    list_b.sort();
+    println!(
+        "part1: {}",
+        list_a
+            .iter()
+            .zip(list_b.iter())
+            .map(|p| (p.0 - p.1).abs())
+            .sum::<i64>()
+    );
+    let mut frequencies: HashMap<i64, i64> = HashMap::new();
+    for n in list_b {
+        *frequencies.entry(n).or_default() += 1;
+    }
+    println!(
+        "part2: {}",
+        list_a
+            .into_iter()
+            .map(|n| n * frequencies.get(&n).copied().unwrap_or_default())
+            .sum::<i64>()
+    );
+    Ok(())
+}