Created
December 5, 2025 15:59
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Solution for Advent of Code 2025 Day 5
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| use std::{ops::RangeInclusive, time::Instant}; | |
| const INPUT: &str = include_str!("inputs/day05.txt"); | |
| fn parse(input: &str) -> (Vec<RangeInclusive<usize>>, impl Iterator<Item = usize>) { | |
| let (ranges, ingredients) = input.split_once("\n\n").unwrap(); | |
| // Collect our ranges. | |
| let ranges = ranges | |
| .lines() | |
| .map(|l| l.split_once('-').unwrap()) | |
| .map(|(l, r)| l.parse().unwrap()..=r.parse().unwrap()) | |
| .collect(); | |
| // Return our ranges and an iterator over our items. | |
| (ranges, ingredients.lines().map(|l| l.parse().unwrap())) | |
| } | |
| fn p1(input: &str) -> usize { | |
| let (ranges, ingredients) = parse(input); | |
| // Count all ingredients that are within any range. | |
| ingredients | |
| .filter(|ingredient| ranges.iter().any(|range| range.contains(ingredient))) | |
| .count() | |
| } | |
| fn p2(input: &str) -> usize { | |
| let (mut ranges, _) = parse(input); | |
| // Sort our ranges and then merge them. | |
| ranges.sort_unstable_by_key(|range| *range.start()); | |
| let mut merged = Vec::with_capacity(ranges.len()); | |
| let mut ranges = ranges.into_iter(); | |
| merged.push(ranges.next().unwrap()); | |
| for range in ranges { | |
| let last = merged.last_mut().unwrap(); | |
| // If they don't overlap, we can simply add the new range to our merged list. | |
| if last.end() < range.start() { | |
| merged.push(range); | |
| continue; | |
| } | |
| // Otherwise, merge the ranges. | |
| *last = *last.start()..=*last.end().max(range.end()); | |
| } | |
| // With the merged list we just get the size of each range and sum them. | |
| merged.iter().map(|r| r.end() - r.start() + 1).sum() | |
| } | |
| fn main() { | |
| let now = Instant::now(); | |
| let solution = p1(INPUT); | |
| println!("p1 {:?} {}", now.elapsed(), solution); | |
| let now = Instant::now(); | |
| let solution = p2(INPUT); | |
| println!("p2 {:?} {}", now.elapsed(), solution); | |
| } | |
| #[cfg(test)] | |
| mod tests { | |
| use super::*; | |
| const INPUT: &str = "3-5\n10-14\n16-20\n12-18\n\n1\n5\n8\n11\n17\n32\n"; | |
| #[test] | |
| fn test_p1() { | |
| assert_eq!(p1(INPUT), 3); | |
| } | |
| #[test] | |
| fn test_p2() { | |
| assert_eq!(p2(INPUT), 14); | |
| } | |
| } |
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