AoC-2023/src/days/day5.rs

use std::{path::Path, str::FromStr};

use crate::{error::AdventError, input::read_into};

#[derive(Debug)]
struct RangeMap {
    start: u32,
    dest: u32,
    length: u32,
}

impl RangeMap {
    fn map(self: &Self, input: u32) -> Option<u32> {
        let upper_bound: u64 = self.start as u64 + self.length as u64;
        if input >= self.start && (input as u64) < upper_bound {
            Some(input - self.start + self.dest)
        }
        else {
            None
        }
    }

    fn inverse_map(&self, input: u32) -> Option<u32> {
        let upper_bound: u64 = self.dest as u64 + self.length as u64;
        if input >= self.dest && (input as u64) < upper_bound {
            Some(input - self.dest + self.start)
        }
        else {
            None
        }
    }
}

#[derive(Debug)]
struct Mapping {
    range_maps: Vec<RangeMap>
}

impl Mapping {
    fn map(self: &Self, input: u32) -> u32 {
        for range_map in self.range_maps.iter() {
            match range_map.map(input) {
                Some(x) => return x,
                None => continue
            }
        }
        input
    }

    fn inverse_map(self: &Self, input: u32) -> u32 {
        for range_map in self.range_maps.iter() {
            match range_map.inverse_map(input) {
                Some(x) => return x,
                None => continue
            }
        }
        input 
    }
}

#[derive(Debug)]
struct Almanac {
    seeds: Vec<u32>,
    seed_to_soil_map: Mapping,
    soil_to_fertilizer_map: Mapping,
    fertilizer_to_water_map: Mapping,
    water_to_light_map: Mapping,
    light_to_temperature_map: Mapping,
    temperature_to_humidity_map: Mapping,
    humidity_to_location_map: Mapping
}

impl Almanac {
    fn new() -> Self {
        Almanac {
            seeds: vec![], 
            seed_to_soil_map: Mapping{range_maps: vec![] },
            soil_to_fertilizer_map: Mapping{range_maps: vec![] },
            fertilizer_to_water_map: Mapping{range_maps: vec![] },
            water_to_light_map: Mapping{range_maps: vec![] },
            light_to_temperature_map: Mapping{range_maps: vec![] },
            temperature_to_humidity_map: Mapping{range_maps: vec![] },
            humidity_to_location_map: Mapping{range_maps: vec![] },
        }
    }

    fn find_closest(self: &Self, forward: bool) -> Result<u32, AdventError> {
        let mut total_mapping = vec![
            &self.seed_to_soil_map,
            &self.soil_to_fertilizer_map,
            &self.fertilizer_to_water_map,
            &self.water_to_light_map,
            &self.light_to_temperature_map,
            &self.temperature_to_humidity_map,
            &self.humidity_to_location_map,
        ];
        
        if forward {
            self.seeds.iter().map(|seed| {
                total_mapping
                .iter()
                .fold(*seed, | input, map| {
                    map.map(input)
                })
            }).min().ok_or(AdventError("mapping procedure went wrong".into()))
        } else {
            total_mapping.reverse();
            for loc in 0..u32::MAX {
                let seed = total_mapping
                .iter()
                .fold(loc, | input, map| {
                    map.inverse_map(input)
                });
                match self.seeds.binary_search(&seed) {
                    Ok(_) => return Ok(loc),
                    Err(_) => continue
                }
            };
            Err(AdventError("Scanned location space, found nothing".into()))
        }
       
    }

    fn interpret_range(self: &mut Self) -> () {
        let mut vec:Vec<u32> = vec![];
        let upper_bound = self.seeds.len() / 2;
        for i in 0..upper_bound {
            for seed in self.seeds[i*2]..self.seeds[i*2]+self.seeds[i*2+1] {
                vec.push(seed);
            }
        }
        vec.sort();
        self.seeds = vec
    }
}

enum State {
    None,
    SeedToSoil,
    SoilToFertilizer,
    FertilizerToWater,
    WaterToLight,
    LightToTemperature,
    TemperatureToHumidity,
    HumidityToLocation,
}

impl FromStr for Almanac {
    type Err = AdventError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        const SEEDS_HEADER: &'static str = "seeds: ";
        const SEED_TO_SOIL_MAP_HEADER: &'static str = "seed-to-soil map:";
        const SOIL_TO_FERTILIZER_MAP_HEADER: &'static str = "soil-to-fertilizer map:";
        const FERTILIZER_TO_WATER_MAP_HEADER: &'static str = "fertilizer-to-water map:";
        const WATER_TO_LIGHT_MAP_HEADER: &'static str = "water-to-light map:";
        const LIGHT_TO_TEMPERATURE_MAP_HEADER: &'static str = "light-to-temperature map:";
        const TEMPERATURE_TO_HUMIDITY_MAP_HEADER: &'static str = "temperature-to-humidity map:";
        const HUMIDITY_TO_LOCATION_MAP_HEADER: &'static str = "humidity-to-location map:";

        let mut almanac = Almanac::new();
        let mut state = State::None;

        for line in s.lines() {
            if line.trim().is_empty() { continue; }

            if line.starts_with(SEEDS_HEADER) {
                almanac.seeds = line
                    .trim()
                    .split_ascii_whitespace()
                    .skip(1)
                    .map(|s| -> Result<u32, AdventError> {
                        Ok(s.trim().parse::<u32>()?)
                    }).collect::<Result<Vec<u32>, AdventError>>()?;
                continue;
            }

            if !match line.trim() {
                SEED_TO_SOIL_MAP_HEADER => { state = State::SeedToSoil; true }
                SOIL_TO_FERTILIZER_MAP_HEADER => { state = State::SoilToFertilizer; true }
                FERTILIZER_TO_WATER_MAP_HEADER => { state = State::FertilizerToWater; true }
                WATER_TO_LIGHT_MAP_HEADER => { state = State::WaterToLight; true  }
                LIGHT_TO_TEMPERATURE_MAP_HEADER => { state = State::LightToTemperature; true }
                TEMPERATURE_TO_HUMIDITY_MAP_HEADER => { state = State::TemperatureToHumidity; true }
                HUMIDITY_TO_LOCATION_MAP_HEADER => { state = State::HumidityToLocation; true }
                _ => false
            } {
                let mapping = line
                .trim()
                .split_ascii_whitespace()
                .map(|s| -> Result<u32, AdventError> {
                    Ok(s.parse::<u32>()?)
                }).collect::<Result<Vec<u32>, AdventError>>()?;
                let range_map = RangeMap {
                    dest: mapping[0],
                    start: mapping[1],
                    length: mapping[2]
                };

                match state {
                    State::None => Err(AdventError("Not in any state".into())),
                    State::SeedToSoil => Ok(almanac.seed_to_soil_map.range_maps.push(range_map)),
                    State::SoilToFertilizer => Ok(almanac.soil_to_fertilizer_map.range_maps.push(range_map)),
                    State::FertilizerToWater => Ok(almanac.fertilizer_to_water_map.range_maps.push(range_map)),
                    State::WaterToLight => Ok(almanac.water_to_light_map.range_maps.push(range_map)),
                    State::LightToTemperature => Ok(almanac.light_to_temperature_map.range_maps.push(range_map)),
                    State::TemperatureToHumidity => Ok(almanac.temperature_to_humidity_map.range_maps.push(range_map)),
                    State::HumidityToLocation => Ok(almanac.humidity_to_location_map.range_maps.push(range_map)),
                }?
            }
        }

        Ok(almanac)
    }
}

pub fn one() -> Result<u64, AdventError>
{
    let almanac = read_into::<Almanac>(Path::new("resources/input5.txt".into()))?;
    Ok(almanac.find_closest(true)? as u64)
}

pub fn two() -> Result<u64, AdventError>
{
    let mut almanac = read_into::<Almanac>(Path::new("resources/input5.txt".into()))?;
    almanac.interpret_range();
    Ok(almanac.find_closest(false)? as u64)
}