advent-of-code/2023/day5/src/main.rs

use std::collections::HashMap;
use std::fs;

#[derive(Debug)]
struct Range {
    input: usize,
    output: usize,
    offset: usize,
}

#[derive(Debug)]
struct Map {
    ranges: Vec<Range>,
    next: String,
}

fn parse() -> Option<(Vec<usize>, HashMap<String, Map>)> {
    // let contents = fs::read_to_string("./day5.txt").expect("Don't find the file");
    let contents = fs::read_to_string("./input.txt").expect("Don't find the file");

    let mut seeds: Vec<usize> = vec![];
    let mut maps: HashMap<String, Map> = HashMap::new();

    let segments: Vec<&str> = contents.split("\n\n").collect();
    match segments[..] {
        [s, ..] => {
            let segments: Vec<&str> = s.split(':').collect();
            match segments[..] {
                [_, s] => {
                    s.split_whitespace()
                        .map(|x| x.parse::<usize>().unwrap())
                        .collect::<Vec<_>>()
                        .iter()
                        .for_each(|s| seeds.push(*s));
                }
                _ => {
                    return None;
                }
            }
        }

        _ => {
            return None;
        }
    }

    for seg in &segments[1..] {
        let mut ranges: Vec<Range> = vec![];
        let segments: Vec<&str> = seg.split('\n').collect();

        let Some((names, r)) = segments.split_first() else {
            return None;
        };

        let names = names.replace(' ', "-");
        let split = names.split('-').collect::<Vec<_>>();
        let [name, _, next, _] = &split[..] else {
            return None;
        };

        for range in r {
            if range.is_empty() {
                continue;
            }
            let split = range
                .split_whitespace()
                .map(|x| x.parse::<usize>().unwrap())
                .collect::<Vec<_>>();
            match split[..] {
                [output, input, off] => ranges.push(Range {
                    input,
                    output,
                    offset: off,
                }),
                _ => return None,
            }
        }
        maps.insert(
            name.to_string(),
            Map {
                ranges,
                next: next.to_string(),
            },
        );
    }

    // println!("Seeds : {:?}", seeds);
    // println!("Ranges : {:#?}", maps);
    Some((seeds, maps))
}

fn check_range(seed: usize, map: &Map, maps: &HashMap<String, Map>) -> usize {
    for range in &map.ranges {
        let input = range.input;
        let output = range.output;
        let offset = range.offset;

        let min = input;
        let max = input + offset;
        if min <= seed && seed < max {
            let o = seed + output - input;
            let Some(m) = maps.get(&map.next) else {
                return o;
            };
            return check_range(o, m, maps);
        }
    }
    let Some(m) = maps.get(&map.next) else {
        return seed;
    };
    check_range(seed, m, maps)
}

fn puzzle1(seeds: &Vec<usize>, maps: &HashMap<String, Map>) {
    let mut s: Vec<usize> = vec![];
    let map = maps.get("seed").unwrap();

    for seed in seeds {
        s.push(check_range(*seed, map, maps));
    }

    // println!(" Seeds → : {:?}", s);
    let min = s.iter().min().unwrap();
    println!("Puzzle 1 : {:?}", min);
}

fn puzzle2(seeds: Vec<usize>, maps: HashMap<String, Map>) {
    let map = maps.get("seed").unwrap();

    let ranges: Vec<_> = seeds
        .chunks(2)
        .map(|i| std::ops::Range {
            start: i[0],
            end: i[0] + i[1],
        })
        .collect();

    let min: Vec<_> = ranges
        .iter()
        .map(|range| {
            range
                .clone()
                .map(|r| check_range(r, map, &maps))
                .min()
                .unwrap()
        })
        .collect::<Vec<_>>();

    let min = min.iter().min().unwrap();
    println!("Puzzle 2 : {:?}", min);
}

fn main() {
    let Some((seeds, maps)) = parse() else {
        panic!("Fail input parsing")
    };

    puzzle1(&seeds, &maps);
    puzzle2(seeds, maps);
}