Year 2025 Day 5

Author: maneatingape

README.md

@@ -81,6 +81,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 2 | [Gift Shop](https://adventofcode.com/2025/day/2) | [Source](src/year2025/day02.rs) | 1 |
 | 3 | [Lobby](https://adventofcode.com/2025/day/3) | [Source](src/year2025/day03.rs) | 18 |
 | 4 | [Printing Department](https://adventofcode.com/2025/day/4) | [Source](src/year2025/day04.rs) | 244 |
+| 5 | [Cafeteria](https://adventofcode.com/2025/day/5) | [Source](src/year2025/day05.rs) | 20 |
 
 ## 2024
 

benches/benchmark.rs

@@ -95,5 +95,5 @@ benchmark!(year2024
 );
 
 benchmark!(year2025
-    day01, day02, day03, day04
+    day01, day02, day03, day04, day05
 );

src/lib.rs

@@ -74,5 +74,5 @@ library!(year2024 "Locate the Chief Historian in time for the big Christmas slei
 );
 
 library!(year2025 "Finish the North Pole decorations in time for Christmas."
-    day01, day02, day03, day04
+    day01, day02, day03, day04, day05
 );

src/main.rs

@@ -141,5 +141,5 @@ run!(year2024
 );
 
 run!(year2025
-    day01, day02, day03, day04
+    day01, day02, day03, day04, day05
 );

src/year2025/day05.rs

@@ -0,0 +1,41 @@
+//! # Cafeteria
+use crate::util::iter::*;
+use crate::util::parse::*;
+
+type Input = (usize, u64);
+
+pub fn parse(input: &str) -> Input {
+    let (prefix, suffix) = input.split_once("\n\n").unwrap();
+    let mut ranges: Vec<_> = prefix.iter_unsigned().chunk::<2>().collect();
+    let mut ids: Vec<_> = suffix.iter_unsigned().collect();
+    let mut range = 0..0;
+    let mut merged = Vec::new();
+
+    ranges.sort_unstable();
+    ids.sort_unstable();
+
+    for [from, to] in ranges {
+        if from < range.end {
+            range.end = range.end.max(to + 1);
+        } else {
+            merged.push(range);
+            range = from..to + 1;
+        }
+    }
+
+    merged.push(range);
+
+    let position = |id: u64| ids.binary_search(&id).unwrap_or_else(|e| e);
+    let part_one = merged.iter().map(|range| position(range.end) - position(range.start)).sum();
+    let part_two = merged.iter().map(|range| range.end - range.start).sum();
+
+    (part_one, part_two)
+}
+
+pub fn part1(input: &Input) -> usize {
+    input.0
+}
+
+pub fn part2(input: &Input) -> u64 {
+    input.1
+}

tests/test.rs

@@ -87,5 +87,5 @@ test!(year2024
 );
 
 test!(year2025
-    day01, day02, day03, day04
+    day01, day02, day03, day04, day05
 );

tests/year2025/day05.rs

@@ -0,0 +1,26 @@
+use aoc::year2025::day05::*;
+
+const EXAMPLE: &str = "\
+3-5
+10-14
+16-20
+12-18
+
+1
+5
+8
+11
+17
+32";
+
+#[test]
+fn part1_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part1(&input), 3);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part2(&input), 14);
+}