advent-of-code-2023/src/bin/part05.rs

use std::time;

use rayon::prelude::*;

struct Almanac {
    seeds: Vec<u32>,
    seed_to_soil: Vec<Mapping>,
    soil_to_fertilizer: Vec<Mapping>,
    fertilizer_to_water: Vec<Mapping>,
    water_to_light:Vec<Mapping>,
    light_to_temperature: Vec<Mapping>,
    temperature_to_humidity: Vec<Mapping>,
    humidity_to_location: Vec<Mapping>,
}

impl Almanac {
    fn new() -> Almanac {
        Almanac {
            seeds: Vec::new(),
            seed_to_soil: Vec::new(),
            soil_to_fertilizer: Vec::new(),
            fertilizer_to_water: Vec::new(),
            water_to_light: Vec::new(),
            light_to_temperature: Vec::new(),
            temperature_to_humidity: Vec::new(),
            humidity_to_location: Vec::new(),
        }
    }

    fn get_soil(&self, seed: u32) -> u32 {
        map(seed, &self.seed_to_soil)
    }

    fn get_fertilizer(&self, seed: u32) -> u32 {
        map(self.get_soil(seed), &self.soil_to_fertilizer)
    }

    fn get_water(&self, seed: u32) -> u32 {
        map(self.get_fertilizer(seed), &self.fertilizer_to_water)
    }

    fn get_light(&self, seed: u32) -> u32 {
        map(self.get_water(seed), &self.water_to_light)
    }

    fn get_temperature(&self, seed: u32) -> u32 {
        map(self.get_light(seed), &self.light_to_temperature)
    }

    fn get_humidity(&self, seed: u32) -> u32 {
        map(self.get_temperature(seed), &self.temperature_to_humidity)
    }

    fn get_location(&self, seed: u32) -> u32 {
        map(self.get_humidity(seed), &self.humidity_to_location)
    }
}

struct Mapping {
    dst_range_start: u64,
    src_range_start: u64,
    range_length: u64
}

fn main() {
    let s = time::Instant::now();

    let almanac = load_input();
    let mut locations: Vec<u32> = Vec::new();

    // for seed in &almanac.seeds {
    //     let location = almanac.get_location(*seed);
    //     locations.push(location);

    //     println!("Seed: {}", seed);
    //     println!("Location: {}", location);
    //     println!();
    // }

    // println!("Lowest location #1: {}", locations.iter().min().unwrap());
    // locations.clear();

    let mut seeds = almanac.seeds.iter();
    loop {
        let seed_start = seeds.next().unwrap_or(&0);
        if *seed_start == 0 {
            break;
        }
        let seed_end = seed_start + seeds.next().unwrap();
        let seed_count = seed_end - seed_start;

        let s1 = time::Instant::now();

        let locs = (*seed_start..seed_end).into_par_iter().map(|seed| {
            almanac.get_location(seed)
        });
        locations.push(locs.min().unwrap());

        let d1 = time::Instant::now().duration_since(s1);
        println!("Parsed {} seeds in {:?} ({} seeds/s)", seed_count, d1, seed_count as f64 / d1.as_secs_f64());
    }

    let d = time::Instant::now().duration_since(s);
    println!("Parsed in {:?}", d);

    println!("Lowest location #2: {}", locations.iter().min().unwrap());
}

fn load_input() -> Almanac {
    let mut almanac = Almanac::new();

    let data = std::fs::read_to_string("src/bin/part05.txt")
                                .expect("Could not read file");
    let mut lines = data.lines();

    almanac.seeds = lines.next().unwrap().split(": ").last().unwrap().split_whitespace().map(|s| s.parse::<u32>().unwrap()).collect::<Vec<_>>();
    almanac.seed_to_soil = parse_map(&mut lines);
    almanac.soil_to_fertilizer = parse_map(&mut lines);
    almanac.fertilizer_to_water = parse_map(&mut lines);
    almanac.water_to_light = parse_map(&mut lines);
    almanac.light_to_temperature = parse_map(&mut lines);
    almanac.temperature_to_humidity = parse_map(&mut lines);
    almanac.humidity_to_location = parse_map(&mut lines);

    almanac
}

fn parse_map(line_iter: &mut dyn Iterator<Item=&str>) -> Vec<Mapping> {
    let mut mappings = Vec::new();

    line_iter.nth(0);

    loop {
        let line = line_iter.next().unwrap_or("");
        if line.is_empty() {
            break;
        } else if line.ends_with(":") {
            continue;
        }
        let mut raw_mapping = line.split_whitespace();
        mappings.push(Mapping {
            dst_range_start: raw_mapping.next().unwrap().parse::<u64>().unwrap(),
            src_range_start: raw_mapping.next().unwrap().parse::<u64>().unwrap(),
            range_length: raw_mapping.next().unwrap().parse::<u64>().unwrap()
        });
    }

    mappings.sort_by(|a, b| b.src_range_start.cmp(&a.src_range_start));

    mappings
}

fn map(src: u32, mappings: &Vec<Mapping>) -> u32 {
    let src = src as u64;
    let mut dst = src;

    let mapping = mappings.iter().find(|mapping| {
        src >= mapping.src_range_start && src < mapping.src_range_start + mapping.range_length
    });

    if let Some(mapping) = mapping {
        dst = (mapping.dst_range_start + src) - mapping.src_range_start;
    }

    dst as u32
}