65 lines
1.7 KiB
Rust
65 lines
1.7 KiB
Rust
|
use std::collections::HashSet;
|
||
|
|
|
||
|
|
use aoc_runner_derive::{aoc as aoc_run, aoc_generator};
|
||
|
|
|
||
|
|
type Position = (i32, i32);
|
||
|
|
|
||
|
|
#[aoc_generator(day9)]
|
||
|
|
fn parse_input(input: &str) -> Vec<Position> {
|
||
|
|
let mut out = Vec::new();
|
||
|
|
let (mut x, mut y) = (0, 0);
|
||
|
|
out.push((x, y));
|
||
|
|
for line in input.lines() {
|
||
|
|
let mut split = line.split_ascii_whitespace();
|
||
|
|
let dir = split.next().unwrap();
|
||
|
|
let num: i32 = split.next().unwrap().parse().unwrap();
|
||
|
|
for _ in 0..num {
|
||
|
|
match dir {
|
||
|
|
"U" => y += 1,
|
||
|
|
"D" => y -= 1,
|
||
|
|
"L" => x -= 1,
|
||
|
|
"R" => x += 1,
|
||
|
|
_ => unreachable!(),
|
||
|
|
}
|
||
|
|
out.push((x, y));
|
||
|
|
}
|
||
|
|
}
|
||
|
|
out
|
||
|
|
}
|
||
|
|
|
||
|
|
#[aoc_run(day9, part1)]
|
||
|
|
fn part1(input: &[Position]) -> usize {
|
||
|
|
let mut tail = (0, 0);
|
||
|
|
let mut set = HashSet::new();
|
||
|
|
set.insert(tail);
|
||
|
|
for mv in input {
|
||
|
|
tail = new_tail(mv, &tail);
|
||
|
|
set.insert(tail);
|
||
|
|
}
|
||
|
|
|
||
|
|
set.len()
|
||
|
|
}
|
||
|
|
|
||
|
|
#[aoc_run(day9, part2)]
|
||
|
|
fn part2(input: &[Position]) -> u32 {
|
||
|
|
0
|
||
|
|
}
|
||
|
|
|
||
|
|
fn new_tail(head: &Position, tail: &Position) -> Position {
|
||
|
|
let dy = head.1 - tail.1;
|
||
|
|
let dx = head.0 - tail.0;
|
||
|
|
match (dx, dy) {
|
||
|
|
(0, 0) => *tail,
|
||
|
|
(n, m) if (n.abs() == 1) && (m.abs() == 1) => *tail,
|
||
|
|
(n, 0) | (0, n) if n.abs() == 1 => *tail,
|
||
|
|
(_, 2) | (_, -2) if dx.abs() == 1 => (tail.0 + dx, tail.1 + (dy / 2)),
|
||
|
|
(2, y) | (-2, y) if y.abs() == 1 => {
|
||
|
|
let sign = dx / dx.abs();
|
||
|
|
(tail.0 + sign * (dx.abs() - 1), tail.1 + dy)
|
||
|
|
}
|
||
|
|
(n, _) if n.abs() == 2 => (tail.0 + n / 2, tail.1),
|
||
|
|
(_, n) if n.abs() == 2 => (tail.0, tail.1 + n / 2),
|
||
|
|
_ => unreachable!("got {:?}", (dx, dy)),
|
||
|
|
}
|
||
|
|
}
|