pastemyst | aoc day 9. late this time

aoc day 9. late this time

main.rs

Rustcopy raw

use std::{io::{stdin, Read}, collections::HashSet};

fn main() {
    let mut stdin = stdin();
    let mut buf: String = String::new();
    stdin.read_to_string(&mut buf).unwrap();

let mut visited: HashSet<Point> = HashSet::new();
    let mut head: Point = Point::new(0, 0);
    // let mut tail: Point = head;
    let mut tails: [Point; 9] = [head; 9];
    for line in buf.split("\n") {
        let dir = match line.chars().next().unwrap() {
            'U' => Point::new(0, 1),
            'D' => Point::new(0, -1),
            'L' => Point::new(-1, 0),
            'R' => Point::new(1, 0),
            _ => Point::new(0, 0)
        };
        let num = line[2..].parse::<i32>().unwrap();
        for _ in 0..num {
            // visited.insert(tail);
            // let (h, t) = mov(head, tail, dir);
            // head = h; tail = t;
            visited.insert(tails[8]);
            let (h, ts) = mov2(head, tails, dir);
            head = h; tails = ts;
        }
    }
    // visited.insert(tail);
    visited.insert(tails[8]);
    println!("{}", visited.len());
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
struct Point {
    x: i32,
    y: i32
}

impl Point {
    fn new(x: i32, y: i32) -> Self {
        Self { x, y }
    }
}

// fn mov(head: Point, tail: Point, by: Point) -> (Point, Point) { // update tail (p1)
//     let new_head = Point::new(head.x + by.x, head.y + by.y);
//     let new_tail = if (new_head.x - tail.x).pow(2) > 1 || (new_head.y - tail.y).pow(2) > 1 {
//         head
//     } else { tail };
//     return (new_head, new_tail);
// }

fn mov2(head: Point, tails: [Point; 9], by: Point) -> (Point, [Point; 9]) { // update tails (p2)
    let new_head = Point::new(head.x + by.x, head.y + by.y);
    let mut new_tails: [Point; 9] = [Point::new(0, 0); 9];
    for i in 0..9 {
        let last_tail = tails[i];
        let h = if i == 0 { new_head } else { new_tails[i-1] };
        let diff = Point::new(h.x - last_tail.x, h.y - last_tail.y);
        new_tails[i] = if diff.x.pow(2) > 1 || diff.y.pow(2) > 1 { // this is clearly the best way to go about things
            Point::new(last_tail.x + diff.x.signum(), last_tail.y + diff.y.signum()) // seems to work ok enough
        } else { last_tail };
    }
    (new_head, new_tails)
}

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stats: 67 lines, 327 words, 2.28kb