#[path = "../lib.rs"] mod lib;

use std::collections::HashSet;

fn simulate(len: usize) -> usize {
    let mut rope: Vec<(i64, i64)> = vec![(0, 0); len];
    let mut visited = HashSet::new();

    for line in lib::iter_input() {
        let (dir, steps_s) = lib::split_once(&line, ' ').unwrap();
        let steps = steps_s.parse::<u64>().unwrap();

        for _ in 0..steps {
            match dir {
                "U" => { rope[len - 1].1 += 1; },
                "D" => { rope[len - 1].1 -= 1; },
                "L" => { rope[len - 1].0 -= 1; },
                "R" => { rope[len - 1].0 += 1; },
                _ => unreachable!(),
            }

            for i1 in (0..len - 1).rev() {
                let i2 = i1 + 1;
                if (rope[i2].0 - rope[i1].0).abs() > 1 || (rope[i2].1 - rope[i1].1).abs() > 1 {
                    if rope[i1].0 < rope[i2].0 {
                        rope[i1].0 += 1;
                    } else if rope[i1].0 > rope[i2].0 {
                        rope[i1].0 -= 1;
                    }
                    if rope[i1].1 < rope[i2].1 {
                        rope[i1].1 += 1;
                    } else if rope[i1].1 > rope[i2].1 {
                        rope[i1].1 -= 1;
                    }
                }
            }

            visited.insert(rope[0]);
        }
    }
    return visited.len();
}

fn main() {
    println!("part1: {}", simulate(2));
    println!("part2: {}", simulate(10));
}