From 4df3715c5dde0d54eb20ac9f5181175ec3d3bc7f Mon Sep 17 00:00:00 2001
From: uku <hi@uku.moe>
Date: Sun, 1 Dec 2024 15:25:51 +0100
Subject: [PATCH] feat(day1): init

---
 Cargo.lock              | 16 +++++++++
 Cargo.toml              |  1 +
 src/solutions/day_01.rs | 74 +++++++++++++++++++++++++++++++++++++++++
 src/solutions/mod.rs    |  4 ++-
 4 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 src/solutions/day_01.rs

diff --git a/Cargo.lock b/Cargo.lock
index 7a29374..1e60d8b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -14,6 +14,7 @@ version = "0.1.0"
 dependencies = [
  "dotenvy",
  "indoc",
+ "itertools",
  "ureq",
 ]
 
@@ -64,6 +65,12 @@ version = "0.15.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1aaf95b3e5c8f23aa320147307562d361db0ae0d51242340f558153b4eb2439b"
 
+[[package]]
+name = "either"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
+
 [[package]]
 name = "flate2"
 version = "1.0.35"
@@ -239,6 +246,15 @@ version = "2.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b248f5224d1d606005e02c97f5aa4e88eeb230488bcc03bc9ca4d7991399f2b5"
 
+[[package]]
+name = "itertools"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.167"
diff --git a/Cargo.toml b/Cargo.toml
index 68c6878..35d95d8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,4 +6,5 @@ edition = "2021"
 [dependencies]
 dotenvy = "0.15.7"
 indoc = "2.0.5"
+itertools = "0.13.0"
 ureq = "2.11.0"
diff --git a/src/solutions/day_01.rs b/src/solutions/day_01.rs
new file mode 100644
index 0000000..0f1ae7a
--- /dev/null
+++ b/src/solutions/day_01.rs
@@ -0,0 +1,74 @@
+use itertools::Itertools;
+
+use crate::common::{Answer, Solution};
+
+pub struct Day01;
+
+impl Solution for Day01 {
+    fn name(&self) -> &'static str {
+        "Historian Hysteria"
+    }
+
+    fn part_a(&self, input: &str) -> Answer {
+        let (mut left, mut right) = input
+            .lines()
+            .map(|l| l.split_once("   ").unwrap())
+            .map(|(n1, n2)| (n1.parse::<i32>().unwrap(), n2.parse::<i32>().unwrap()))
+            .collect::<(Vec<_>, Vec<_>)>();
+
+        left.sort();
+        right.sort();
+
+        let sum: i32 = left
+            .into_iter()
+            .zip(right)
+            .map(|(a, b)| (a - b).abs())
+            .sum();
+
+        Answer::Number(sum as u64)
+    }
+
+    fn part_b(&self, input: &str) -> Answer {
+        let (left, right) = input
+            .lines()
+            .map(|l| l.split_once("   ").unwrap())
+            .map(|(n1, n2)| (n1.parse::<i32>().unwrap(), n2.parse::<i32>().unwrap()))
+            .collect::<(Vec<_>, Vec<_>)>();
+
+        let counts = right.into_iter().counts();
+
+        let sum = left
+            .into_iter()
+            .map(|n| counts.get(&n).unwrap_or(&0) * (n as usize))
+            .sum::<usize>();
+
+        Answer::Number(sum as u64)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::Day01;
+    use crate::common::Solution;
+
+    use indoc::indoc;
+
+    const INPUT: &str = indoc! {"
+        3   4
+        4   3
+        2   5
+        1   3
+        3   9
+        3   3
+    "};
+
+    #[test]
+    fn part_a() {
+        assert_eq!(Day01.part_a(INPUT), 11.into());
+    }
+
+    #[test]
+    fn part_b() {
+        assert_eq!(Day01.part_b(INPUT), 31.into());
+    }
+}
diff --git a/src/solutions/mod.rs b/src/solutions/mod.rs
index 24ed351..ded8423 100644
--- a/src/solutions/mod.rs
+++ b/src/solutions/mod.rs
@@ -1,3 +1,5 @@
 use crate::common::Solution;
 
-pub const SOLUTIONS: &[&dyn Solution] = &[];
+mod day_01;
+
+pub const SOLUTIONS: &[&dyn Solution] = &[&day_01::Day01];