From 509f796a52c67e462e79781ebc26ec4545f5feb2 Mon Sep 17 00:00:00 2001
From: Bauke <me@bauke.xyz>
Date: Tue, 7 Dec 2021 14:24:37 +0100
Subject: [PATCH] Solve day 7!

---
 source/day_07/mod.rs | 49 ++++++++++++++++++++++++++++++++++++++++++++
 source/main.rs       |  2 ++
 2 files changed, 51 insertions(+)
 create mode 100644 source/day_07/mod.rs

diff --git a/source/day_07/mod.rs b/source/day_07/mod.rs
new file mode 100644
index 0000000..71090f5
--- /dev/null
+++ b/source/day_07/mod.rs
@@ -0,0 +1,49 @@
+use color_eyre::{eyre::eyre, Result};
+
+pub fn solve() -> Result<()> {
+  let input_data = include_str!("../../data/day_07.txt").trim();
+  println!("Day 07 Part 1: {}", part_1(input_data)?);
+  println!("Day 07 Part 2: {}", part_2(input_data)?);
+  Ok(())
+}
+
+fn parse_crabs(input: &str) -> Result<(Vec<isize>, isize)> {
+  let crabs = input
+    .split(",")
+    .map(str::parse)
+    .collect::<Result<Vec<_>, _>>()?;
+
+  let highest_crab = *crabs
+    .iter()
+    .max()
+    .ok_or(eyre!("Unable to find highest crab"))?;
+
+  Ok((crabs, highest_crab))
+}
+
+fn part_1(input: &str) -> Result<isize> {
+  let (crabs, highest_crab) = parse_crabs(input)?;
+  (0..=highest_crab)
+    .map(|target_position| {
+      crabs
+        .iter()
+        .map(|crab| (target_position - crab).abs())
+        .sum()
+    })
+    .min()
+    .ok_or(eyre!("Unable to find lowest fuel"))
+}
+
+fn part_2(input: &str) -> Result<isize> {
+  let (crabs, highest_crab) = parse_crabs(input)?;
+  (0..=highest_crab)
+    .map(|target_position| {
+      crabs
+        .iter()
+        .map(|crab| (target_position - crab).abs())
+        .map(|steps| (steps * (steps + 1)) / 2)
+        .sum()
+    })
+    .min()
+    .ok_or(eyre!("Unable to find lowest fuel"))
+}
diff --git a/source/main.rs b/source/main.rs
index bcad1e2..baef111 100644
--- a/source/main.rs
+++ b/source/main.rs
@@ -8,6 +8,7 @@ mod day_03;
 mod day_04;
 mod day_05;
 mod day_06;
+mod day_07;
 
 fn main() -> Result<()> {
   color_eyre::install()?;
@@ -21,6 +22,7 @@ fn main() -> Result<()> {
     day_04::solve,
     day_05::solve,
     day_06::solve,
+    day_07::solve,
   ];
 
   for day in days {