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use std::{ops::Range, str::FromStr};
use anyhow::Context;
use crate::{Problem, Solution};
pub struct Day05;
impl Problem for Day05 {
const DAY: u8 = 5;
const INPUT: &'static str = include_str!("../input/day_05.txt");
}
impl Solution for Day05 {
type Answer1 = usize;
type Answer2 = usize;
fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
let (first, rest) = input
.trim()
.split_once('\n')
.context("Missing value map label")?;
let mut seeds = first
.strip_prefix("seeds: ")
.context("Failed to get seeds")?
.split_whitespace()
.map(FromStr::from_str)
.try_collect::<Vec<usize>>()?
.into_iter()
.map(|n| n..(n + 1))
.collect::<Vec<_>>();
for set in rest
.trim()
.split("\n\n")
.map(FromStr::from_str)
.try_collect::<Vec<ValueMapSet>>()?
{
seeds = seeds
.into_iter()
.flat_map(|seed_range| set.transform(seed_range))
.collect();
}
seeds
.iter()
.map(|range| range.start)
.min()
.context("Failed to find min seed")
}
fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
let (first, rest) = input
.trim()
.split_once('\n')
.context("Missing value map label")?;
let mut seeds = first
.strip_prefix("seeds: ")
.context("Failed to get seeds")?
.split_whitespace()
.map(FromStr::from_str)
.try_collect::<Vec<usize>>()?
.into_iter()
.array_chunks()
.map(|[n, len]| n..(n + len))
.collect::<Vec<_>>();
for set in rest
.trim()
.split("\n\n")
.map(FromStr::from_str)
.try_collect::<Vec<ValueMapSet>>()?
{
seeds = seeds
.into_iter()
.flat_map(|seed_range| set.transform(seed_range))
.collect();
}
seeds
.iter()
.map(|range| range.start)
.min()
.context("Failed to find min seed")
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct ValueMap {
dest: usize,
src: usize,
length: usize,
}
impl ValueMap {
fn intersect(&self, seed: &Range<usize>) -> Range<usize> {
seed.start.max(self.src)..seed.end.min(self.src + self.length)
}
}
impl FromStr for ValueMap {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let Some([Ok(dest), Ok(src), Ok(length)]) = s
.split_whitespace()
.map(FromStr::from_str)
.array_chunks()
.next()
else {
anyhow::bail!("Invalid value map range");
};
Ok(Self { dest, src, length })
}
}
struct ValueMapSet(Vec<ValueMap>);
impl ValueMapSet {
fn transform(&self, seed_range: Range<usize>) -> Vec<Range<usize>> {
let mut queue = Vec::from([seed_range]);
let mut mapped = Vec::new();
while let Some(seed) = queue.pop() {
let Some(&map) = self.0.iter().find(|t| !t.intersect(&seed).is_empty()) else {
mapped.push(seed);
continue;
};
let intersect = map.intersect(&seed);
mapped.push(Range {
start: (intersect.start + map.dest) - map.src,
end: (intersect.end + map.dest) - map.src,
});
if seed.start < map.src {
queue.push(Range {
start: seed.start,
end: intersect.start - 1,
});
}
if seed.end > (map.src + map.length) {
queue.push(Range {
start: intersect.end + 1,
end: seed.end,
});
}
}
mapped.into_iter().collect()
}
}
impl FromStr for ValueMapSet {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
s.trim()
.lines()
.skip(1)
.map(FromStr::from_str)
.try_collect::<Vec<ValueMap>>()
.map(Self)
}
}
#[cfg(test)]
mod tests {
use super::*;
const INPUT: &str = indoc::indoc! {"
seeds: 79 14 55 13
seed-to-soil map:
50 98 2
52 50 48
soil-to-fertilizer map:
0 15 37
37 52 2
39 0 15
fertilizer-to-water map:
49 53 8
0 11 42
42 0 7
57 7 4
water-to-light map:
88 18 7
18 25 70
light-to-temperature map:
45 77 23
81 45 19
68 64 13
temperature-to-humidity map:
0 69 1
1 0 69
humidity-to-location map:
60 56 37
56 93 4
"};
#[test]
fn test_part_1() -> anyhow::Result<()> {
Ok(assert_eq!(35, Day05::part_1(INPUT)?))
}
#[test]
fn test_part_2() -> anyhow::Result<()> {
Ok(assert_eq!(46, Day05::part_2(INPUT)?))
}
}
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