use std::fs;
use std::path::Path;
use std::collections::HashMap;

/* AOC21 Day 12: https://adventofcode.com/2021/day/12 */
fn main() {
    let input = Path::new("resources").join("input.txt");
    let content = fs::read_to_string(input).expect("Unable to read input file");
    let mut adj = HashMap::<&str,Vec<&str>>::new();
    content.lines()
           .map(|l| l.split_once('-').expect("Malformed input"))
           .for_each(|(from,to)| {
                adj.entry(from).or_default().push(to);
                adj.entry(to).or_default().push(from);
            });
    println!("Ex1: the result is {}", genpath(&mut vec!["start"], &adj));
    println!("Ex2: the result is {}", genpath_rep(&mut vec!["start"], &adj));
}

fn genpath<'a>(path: &mut Vec<&'a str>, adj: &HashMap<&str,Vec<&'a str>>) -> u32 {
    let last = path.last().unwrap();
    if *last == "end" { 1 } else {
        let mut paths = 0;
        if let Some(vec) = adj.get(last) {
            let next: Vec<&str> = vec.iter().filter(|n| n.chars().all(|c| c.is_uppercase()) || !path.contains(&n)).cloned().collect();
            for n in next {
                path.push(n);
                paths += genpath(path, adj);
                path.pop();
            }
        }
        paths
    }
}

fn genpath_rep<'a>(path: &mut Vec<&'a str>, adj: &HashMap<&str,Vec<&'a str>>) -> u32 {
    let last = path.last().unwrap();
    if *last == "end" { 1 } else {
        let mut paths = 0;
        if let Some(vec) = adj.get(last) {
            for n in vec.iter().filter(|&n| *n != "start") {
                if n.chars().all(|c| c.is_lowercase()) && path.contains(n) {
                    path.push(n);
                    paths += genpath(path, adj);
                } else {
                    path.push(n);
                    paths += genpath_rep(path, adj);
                }
                path.pop();
            }
        }
        paths
    }
}