2022 rust day 9
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@ -1,3 +1,4 @@
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#![allow(dead_code)]
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use std::collections::HashSet;
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use crate::utils;
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@ -19,45 +20,48 @@ struct Move {
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}
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fn fix_tail(head: (i32, i32), tail: (i32, i32), direction: &Direction) -> Option<(i32, i32)> {
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let diff_x = head.0.abs_diff(tail.0);
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let diff_y = head.1.abs_diff(tail.1);
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match (diff_y > 1, diff_x > 1, direction) {
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(true, _, Direction::U) => Some((head.0, head.1 - 1)),
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(true, _, Direction::D) => Some((head.0, head.1 + 1)),
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(_, true, Direction::L) => Some((head.0 + 1, head.1)),
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(_, true, Direction::R) => Some((head.0 - 1, head.1)),
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(_, _, _) => None,
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#[inline(always)]
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fn fix_tail(head: (i32, i32), tail: (i32, i32)) -> (i32, i32) {
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let diff_x = tail.0 - head.0;
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let diff_y = tail.1 - head.1;
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match (diff_x.abs() > 1, diff_y.abs() > 1) {
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(true, true) => (head.0 + diff_x.signum(), head.1 + diff_y.signum()),
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(true, false) => (head.0 + diff_x.signum(), head.1),
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(false, true) => (head.0, head.1 + diff_y.signum()),
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_ => tail,
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}
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}
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fn tail_visits(data: &[Move]) -> HashSet<(i32, i32)> {
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let mut set = HashSet::from([(0, 0)]);
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let mut head = (0, 0);
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let mut tail = (0, 0);
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fn tail_visits(data: &[Move], knots: &mut [(i32, i32)]) -> HashSet<(i32, i32)> {
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let mut set = HashSet::from([*knots.last().unwrap()]);
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for m in data {
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for _ in 0..m.units {
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match m.direction {
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Direction::U => head = (head.0, head.1 + 1),
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Direction::D => head = (head.0, head.1 - 1),
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Direction::L => head = (head.0 - 1, head.1),
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Direction::R => head = (head.0 + 1, head.1),
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}
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if let Some(new) = fix_tail(head, tail, &m.direction) {
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set.insert(new);
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tail = new
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// First move the head
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let head = knots[0];
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knots[0] = match m.direction {
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Direction::U => (head.0, head.1 + 1),
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Direction::D => (head.0, head.1 - 1),
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Direction::L => (head.0 - 1, head.1),
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Direction::R => (head.0 + 1, head.1),
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};
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// Second fix all knots sequentially for arbitrary number of knots
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for idx in 1..knots.len() {
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knots[idx] = fix_tail(knots[idx-1], knots[idx]);
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}
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set.insert(*knots.last().unwrap());
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}
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};
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set
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}
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fn solve1(data: &[Move]) -> usize {
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tail_visits(&data).len()
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let mut knots = [(0, 0); 2];
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tail_visits(&data, &mut knots).len()
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}
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fn solve2(data: &[Move]) -> i32 {
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2
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fn solve2(data: &[Move]) -> usize {
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let mut knots = [(0, 0); 10];
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tail_visits(&data, &mut knots).len()
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}
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@ -84,17 +88,17 @@ fn parse_data<T: AsRef<str>>(data: &[T]) -> Vec<Move> {
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mod tests {
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use super::*;
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static DATA: &[&str; 8] = &["R 4", "U 4", "L 3", "D 1", "R 4", "D 1", "L 5", "R 2"];
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static DATA_A: &[&str; 8] = &["R 4", "U 4", "L 3", "D 1", "R 4", "D 1", "L 5", "R 2"];
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static DATA_B: &[&str; 8] = &["R 5", "U 8", "L 8", "D 3", "R 17", "D 10", "L 25", "U 20"];
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#[test]
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fn part1() {
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let data = parse_data(DATA);
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assert_eq!(13, solve1(&data));
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assert_eq!(13, solve1(&parse_data(DATA_A)));
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}
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#[test]
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fn part2() {
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let data = parse_data(DATA);
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assert_eq!(2, solve2(&data));
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assert_eq!(1, solve2(&parse_data(DATA_A)));
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assert_eq!(36, solve2(&parse_data(DATA_B)));
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}
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}
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