day5: part2

README.md

@@ -1,6 +1,6 @@
 <!-- AOC TILES BEGIN -->
 <h1 align="center">
-  2025 - 9 ⭐ - Rust
+  2025 - 10 ⭐ - Rust
 </h1>
 <a href="src/day1.rs">
   <img src=".aoc_tiles/tiles/2025/01.png" width="161px">

src/day5.rs

@@ -1,3 +1,5 @@
+use std::cmp::{max, min};
+use std::fmt::Debug;
 use std::ops::RangeInclusive;
 
 use aoc_runner_derive::{aoc, aoc_generator};
@@ -7,18 +9,94 @@ struct Database {
     available_ingredients: Vec<u64>,
 }
 
-#[aoc_generator(day5)]
+struct Database2 {
+    fresh_ingredients: Vec<Span>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Span {
+    start: u64,
+    end: u64,
+}
+
+impl From<(u64, u64)> for Span {
+    fn from(value: (u64, u64)) -> Self {
+        Self {
+            start: value.0,
+            end: value.1,
+        }
+    }
+}
+
+impl Span {
+    fn len(&self) -> u64 {
+        self.end - self.start + 1
+    }
+}
+
+struct RangeSet {
+    ranges: Vec<Span>,
+}
+
+impl RangeSet {
+    fn new() -> Self {
+        Self { ranges: Vec::new() }
+    }
+    fn simplify(&mut self) {
+        // sort the ranges by start
+        if self.ranges.len() < 2 {
+            return;
+        }
+        let mut modified = true;
+        while modified {
+            let mut new_ranges = Vec::new();
+            modified = false;
+            self.ranges.sort_by_key(|s| s.start);
+            for chunk in self.ranges.chunks(2) {
+                if chunk.len() == 1 {
+                    new_ranges.push(chunk[0].clone());
+                    continue;
+                }
+                let (l, r) = (&chunk[0], &chunk[1]);
+                if r.start <= l.end + 1 {
+                    modified = true;
+                    new_ranges.push((min(r.start, l.start), max(l.end, r.end)).into())
+                } else {
+                    new_ranges.push(l.clone());
+                    new_ranges.push(r.clone());
+                }
+            }
+            if !self.ranges.len().is_multiple_of(2) && new_ranges.len() >= 2 {
+                let (l, r) = (new_ranges.pop().unwrap(), new_ranges.pop().unwrap());
+                if r.start <= l.end + 1 && r.end >= l.start - 1 {
+                    modified = true;
+                    new_ranges.push((min(r.start, l.start), max(l.end, r.end)).into())
+                } else {
+                    new_ranges.push(l.clone());
+                    new_ranges.push(r.clone());
+                }
+            }
+            self.ranges = new_ranges;
+        }
+    }
+    fn add(&mut self, s: Span) {
+        self.ranges.push(s);
+        self.simplify()
+    }
+}
+
+#[aoc_generator(day5, part1)]
 fn parse(input: &str) -> Database {
     let mut fresh_ingredients = Vec::new();
     let mut available_ingredients = Vec::new();
     let mut parsing_ranges = true;
     for line in input.lines() {
-        if line == "" {
+        if line.is_empty() {
             parsing_ranges = false;
             continue;
         }
         if parsing_ranges {
-            let (start, end) = line.split_once(|c| c == '-').unwrap();
+            let (start, end) = line.split_once('-').unwrap();
             fresh_ingredients.push(RangeInclusive::new(
                 start.parse().unwrap(),
                 end.parse().unwrap(),
@@ -33,6 +111,19 @@ fn parse(input: &str) -> Database {
     }
 }
 
+#[aoc_generator(day5, part2)]
+fn parse2(input: &str) -> Database2 {
+    let mut fresh_ingredients = Vec::new();
+    for line in input.lines() {
+        if line.is_empty() {
+            return Database2 { fresh_ingredients };
+        }
+        let (start, end) = line.split_once('-').unwrap();
+        fresh_ingredients.push((start.parse().unwrap(), end.parse().unwrap()).into());
+    }
+    Database2 { fresh_ingredients }
+}
+
 #[aoc(day5, part1)]
 fn part1(input: &Database) -> u64 {
     input
@@ -43,8 +134,13 @@ fn part1(input: &Database) -> u64 {
 }
 
 #[aoc(day5, part2)]
-fn part2(input: &Database) -> u64 {
-    0
+fn part2(input: &Database2) -> u64 {
+    let mut all_ingredients = RangeSet::new();
+    for r in &input.fresh_ingredients {
+        all_ingredients.add(r.clone())
+    }
+
+    all_ingredients.ranges.iter().map(|r| r.len()).sum::<u64>()
 }
 
 #[cfg(test)]
@@ -70,6 +166,6 @@ mod tests {
 
     #[test]
     fn part2_example() {
-        assert_eq!(part2(&parse(EXAMPLE)), 0);
+        assert_eq!(part2(&parse2(EXAMPLE)), 14);
     }
 }

src/lib.rs

@@ -2,6 +2,7 @@ mod day1;
 mod day2;
 mod day3;
 mod day4;
+mod day5;
 
 use aoc_runner_derive::aoc_lib;