advent_of_code/year2022/
day09.rs

1use crate::input::Input;
2
3pub fn solve(input: &Input) -> Result<usize, String> {
4    let snake_len = input.part_values(2, 10);
5    let mut snake = vec![(0_i32, 0_i32); snake_len];
6    let mut visited = Vec::with_capacity(input.text.len());
7    visited.push((0_i32, 0_i32));
8
9    for line in input.text.lines().filter(|line| line.len() > 2) {
10        let direction = line.as_bytes()[0];
11        let steps = i32::from(
12            line[2..]
13                .parse::<u8>()
14                .map_err(|_| "Not an integer for steps".to_string())?,
15        );
16
17        match direction {
18            b'U' => snake[0].1 -= steps,
19            b'R' => snake[0].0 += steps,
20            b'D' => snake[0].1 += steps,
21            _ => snake[0].0 -= steps,
22        };
23
24        for _ in 0..steps {
25            for i in 1..snake_len {
26                if snake[i - 1].0.abs_diff(snake[i].0) > 1
27                    || snake[i - 1].1.abs_diff(snake[i].1) > 1
28                {
29                    snake[i].0 += (snake[i - 1].0 - snake[i].0).signum();
30                    snake[i].1 += (snake[i - 1].1 - snake[i].1).signum();
31                    if i + 1 == snake_len {
32                        visited.push(snake[i]);
33                    }
34                }
35            }
36        }
37    }
38
39    visited.sort_unstable();
40    Ok(visited.windows(2).filter(|w| w[0] != w[1]).count() + 1)
41}
42
43#[test]
44pub fn tests() {
45    let test_input = "R 4\nU 4\nL 3\nD 1\nR 4\nD 1\nL 5\nR 2";
46    test_part_one!(test_input => 13);
47    test_part_two!(test_input => 1);
48
49    let test_input = "R 5\nU 8\nL 8\nD 3\nR 17\nD 10\nL 25\nU 20";
50    test_part_two!(test_input => 36);
51
52    let real_input = include_str!("day09_input.txt");
53    test_part_one!(real_input => 6081);
54    test_part_two!(real_input => 2487);
55}
advent_of_code/year2022/day09.rs

advent_of_code/year2022/
day09.rs
