AoC23/src/day05.rs

use std::{collections::HashMap, ops::Range};

use regex::Regex;

pub fn run() {
    let input = include_str!("../input/day5.txt");
    // let input = r#"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"#;

    let almanac = Almanac::parse_seed_list(input);
    let part1 = almanac.convert_seeds_to_locations();
    dbg!(part1.iter().min().unwrap());

    let almanac2 = Almanac::parse_seed_range(input);
    let part2 = almanac2.convert_seeds_to_locations();
    dbg!(part2.iter().min().unwrap());
}

#[derive(Debug, Clone)]
struct Almanac<S: IntoIterator<Item = i64> + Clone> {
    seeds: S,
    maps: HashMap<(String, String), Map>,
}

fn parse_maps<'a>(parts: impl Iterator<Item = &'a str>) -> HashMap<(String, String), Map> {
    let mut maps = HashMap::new();
    let map_name_re = Regex::new(r#"(\w+)-to-(\w+) map:"#).unwrap();
    for map_s in parts {
        let (name, rest) = map_s.split_once("\n").unwrap();
        let map_captures = map_name_re.captures(name).unwrap();
        let map = Map::parse(rest);
        maps.insert(
            (map_captures[1].to_owned(), map_captures[2].to_owned()),
            map,
        );
    }
    maps
}

impl Almanac<Vec<i64>> {
    fn parse_seed_list(s: &str) -> Self {
        let mut parts = s.split("\n\n");
        let seeds_s = parts.next().unwrap();
        assert!(seeds_s.starts_with("seeds: "));
        let seeds_s = seeds_s.split_at("seeds: ".len()).1;
        let seeds = seeds_s
            .split(" ")
            .map(|s| s.parse::<i64>().unwrap())
            .collect::<Vec<_>>();
        Self {
            seeds,
            maps: parse_maps(parts),
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
struct Seeds {
    ranges: Vec<Range<i64>>,
    cur: Option<Range<i64>>,
}

impl Iterator for Seeds {
    type Item = i64;

    fn next(&mut self) -> Option<Self::Item> {
        if self.cur.is_none() || self.cur.as_ref().unwrap().is_empty() {
            if self.ranges.is_empty() {
                self.cur = None;
                return None;
            } else {
                self.cur = Some(self.ranges.remove(0));
                return self.next();
            }
        } else {
            let cur = self.cur.as_ref().unwrap();
            let ret = cur.start;
            self.cur = Some((cur.start + 1)..cur.end);
            return Some(ret);
        }
    }
}

impl Almanac<Seeds> {
    fn parse_seed_range(s: &str) -> Self {
        let mut parts = s.split("\n\n");
        let seeds_s = parts.next().unwrap();
        assert!(seeds_s.starts_with("seeds: "));
        let seeds_s = seeds_s.split_at("seeds: ".len()).1;
        let numbers = seeds_s
            .split(" ")
            .map(|s| s.parse::<i64>().unwrap())
            .collect::<Vec<_>>();
        assert!(numbers.len() % 2 == 0);
        let ranges = numbers
            .chunks(2)
            .map(|chunk| chunk[0]..(chunk[0] + chunk[1]))
            .collect::<Vec<_>>();
        Self {
            seeds: Seeds { ranges, cur: None },
            maps: parse_maps(parts),
        }
    }
}

impl<S: IntoIterator<Item = i64> + Clone> Almanac<S> {
    fn convert(&self, xs: &mut Vec<i64>, from: &str, to: &str) {
        let map = self
            .maps
            .get(&(from.to_owned(), to.to_owned()))
            .expect(&format!("conversion from {} to {}", from, to));
        for i in 0..xs.len() {
            xs[i] = map.convert(xs[i]);
        }
    }

    fn convert_seeds_to_locations(&self) -> Vec<i64> {
        let path = &[
            "soil",
            "fertilizer",
            "water",
            "light",
            "temperature",
            "humidity",
            "location",
        ];
        let mut cur_type = "seed";
        let mut cur = self.seeds.clone().into_iter().collect::<Vec<_>>();
        for next in path {
            self.convert(&mut cur, cur_type, next);
            cur_type = next;
        }
        cur
    }
}

#[derive(Debug, Clone, PartialEq)]
struct Map {
    // range of source and offset to dest
    ranges: Vec<(Range<i64>, i64)>,
}

impl Map {
    fn parse(s: &str) -> Self {
        let ranges = s
            .lines()
            .map(|l| {
                let mut parts = l.trim().split(" ");
                let dest_start: i64 = parts.next().unwrap().parse().unwrap();
                let source_start: i64 = parts.next().unwrap().parse().unwrap();
                let len: i64 = parts.next().unwrap().parse().unwrap();
                assert_eq!(parts.next(), None);
                (
                    source_start..(source_start + len),
                    dest_start - source_start,
                )
            })
            .collect::<Vec<_>>();
        Self { ranges }
    }

    fn convert(&self, source: i64) -> i64 {
        for (range, offset) in self.ranges.iter() {
            if range.contains(&source) {
                return source + offset;
            }
        }
        source
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_parse_map() {
        assert_eq!(
            Map::parse("50 98 2\n52 50 48"),
            Map {
                ranges: vec![(98..100, -48), (50..98, 2),],
            }
        )
    }

    #[test]
    fn test_map_convert() {
        let m = Map {
            ranges: vec![(98..100, -48), (50..98, 2)],
        };
        assert_eq!(m.convert(98), 50);
        assert_eq!(m.convert(53), 55);
        assert_eq!(m.convert(10), 10);
    }

    #[test]
    fn test_parse_almanac() {
        let a = Almanac::parse_seed_list(
            r#"seeds: 79 14 55 13

seed-to-soil map:
50 98 2
52 50 48"#,
        );
        assert_eq!(a.seeds, vec![79, 14, 55, 13]);
        let k = ("seed".to_owned(), "soil".to_owned());
        assert_eq!(a.maps.keys().collect::<Vec<_>>(), vec![&k]);
        assert_eq!(
            a.maps[&k],
            Map {
                ranges: vec![(98..100, -48), (50..98, 2)],
            }
        );
    }

    #[test]
    fn test_parse_almanac_seed_ranges() {
        let a = Almanac::parse_seed_range("seeds: 1 2 3 4");
        assert_eq!(
            a.seeds,
            Seeds {
                ranges: vec![1..3, 3..7],
                cur: None,
            }
        );
    }

    #[test]
    fn test_seeds_iter() {
        assert_eq!(
            Seeds {
                ranges: vec![1..3, 3..7],
                cur: None,
            }
            .collect::<Vec<_>>(),
            vec![1, 2, 3, 4, 5, 6]
        );
    }
}