From 84dba789f80beef344a1c62292601493bd59c189 Mon Sep 17 00:00:00 2001
From: Lars Martens <lars@martens.red>
Date: Thu, 5 Dec 2024 07:42:18 +0100
Subject: [PATCH] Solve 05

---
 src/bin/05.rs | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 src/bin/05.rs

diff --git a/src/bin/05.rs b/src/bin/05.rs
new file mode 100644
index 0000000..7ba7cdc
--- /dev/null
+++ b/src/bin/05.rs
@@ -0,0 +1,115 @@
+use aoc::*;
+
+const INPUT: &str = include_str!("../../input/05");
+
+fn main() {
+    assert_example!(part1, "05-test", 143);
+    println!("Part 1: {}", part1(INPUT));
+    assert_example!(part2, "05-test", 123);
+    println!("Part 2: {}", part2(INPUT));
+}
+
+fn part1(input: &str) -> usize {
+    Puzzle::parse(input).part1()
+}
+
+fn part2(input: &str) -> usize {
+    Puzzle::parse(input).part2()
+}
+
+struct Puzzle {
+    rules: Rules,
+    updates: Vec<Update>,
+}
+
+impl Puzzle {
+    fn part1(self) -> usize {
+        self.updates
+            .iter()
+            .filter(|u| u.valid(&self.rules))
+            .map(Update::middle)
+            .sum()
+    }
+
+    fn part2(self) -> usize {
+        self.updates
+            .into_iter()
+            .filter(|u| !u.valid(&self.rules))
+            .map(|mut u| {
+                u.fix(&self.rules);
+                u.middle()
+            })
+            .sum()
+    }
+
+    fn parse(input: &str) -> Self {
+        let (rules, updates) = input.split_once("\n\n").unwrap();
+        let rules = Rules::parse(rules);
+        let updates = updates.lines().map(Update::parse).collect();
+        Self { rules, updates }
+    }
+}
+
+struct Rules(Vec<Rule>);
+
+impl Rules {
+    fn valid_order(&self, first: usize, second: usize) -> bool {
+        !self
+            .0
+            .iter()
+            .any(|&Rule(before, after)| after == first && before == second)
+    }
+
+    fn parse(input: &str) -> Self {
+        let rules = input.lines().map(Rule::parse).collect();
+        Self(rules)
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+struct Rule(usize, usize);
+
+impl Rule {
+    fn parse(input: &str) -> Self {
+        let (before, after) = input.split_once('|').unwrap();
+        let before = before.parse().unwrap();
+        let after = after.parse().unwrap();
+        Self(before, after)
+    }
+}
+
+#[derive(Debug)]
+struct Update(Vec<usize>);
+
+impl Update {
+    fn valid(&self, rules: &Rules) -> bool {
+        for i in 0..self.0.len() - 1 {
+            for j in i + 1..self.0.len() {
+                if !rules.valid_order(self.0[i], self.0[j]) {
+                    return false;
+                }
+            }
+        }
+        true
+    }
+
+    fn fix(&mut self, rules: &Rules) {
+        for i in 0..self.0.len() - 1 {
+            for j in i + 1..self.0.len() {
+                if !rules.valid_order(self.0[i], self.0[j]) {
+                    self.0.swap(i, j);
+                }
+            }
+        }
+    }
+
+    fn middle(&self) -> usize {
+        let middle = self.0.len() / 2;
+        self.0[middle]
+    }
+
+    fn parse(input: &str) -> Self {
+        let update = input.split(',').map(|n| n.parse().unwrap()).collect();
+        Self(update)
+    }
+}