87 lines
2.4 KiB
Rust
87 lines
2.4 KiB
Rust
#![feature(test)]
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#![allow(clippy::ptr_arg)]
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extern crate test;
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use aoc2020::{common::*, grid::*};
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type Parsed = Vec<(char, i64)>;
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fn read_input() -> String {
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read_file(12)
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}
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fn parse_input(raw: &str) -> Parsed {
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raw.lines()
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.map(|l| (l.bytes().next().unwrap() as char, l[1..].parse().unwrap()))
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.collect()
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}
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fn part1(parsed: &Parsed) -> i64 {
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let end_pos = parsed
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.iter()
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.fold((Direction::Right, PositionND::from([0, 0])), |(dir, pos), (cmd, dist)| match cmd {
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'N' => (dir, pos + PositionND::from([0, *dist])),
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'S' => (dir, pos - PositionND::from([0, *dist])),
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'E' => (dir, pos + PositionND::from([*dist, 0])),
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'W' => (dir, pos - PositionND::from([*dist, 0])),
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'R' => (dir + (dist / 90) as i8, pos),
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'L' => (dir + -(dist / 90) as i8, pos),
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'F' => (dir, pos + PositionND::from(dir) * *dist),
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_ => unreachable!(),
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})
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.1;
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end_pos.points[0].abs() + end_pos.points[1].abs()
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}
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fn rotate_waypoint(mut wp: PositionND<2>, deg: i64) -> PositionND<2> {
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for _ in 0..((deg / 90 + 4) & 3) {
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wp = PositionND::from([wp.points[1], -wp.points[0]]);
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}
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wp
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}
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fn part2(parsed: &Parsed) -> i64 {
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let end_pos = parsed
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.iter()
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.fold(
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(PositionND::from([10, 1]), PositionND::from([0, 0])),
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|(wp, pos), (cmd, dist)| match cmd {
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'N' => (wp + PositionND::from([0, *dist]), pos),
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'S' => (wp - PositionND::from([0, *dist]), pos),
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'E' => (wp + PositionND::from([*dist, 0]), pos),
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'W' => (wp - PositionND::from([*dist, 0]), pos),
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'R' => (rotate_waypoint(wp, *dist), pos),
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'L' => (rotate_waypoint(wp, -dist), pos),
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'F' => (wp, pos + wp * *dist),
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_ => unreachable!(),
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},
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)
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.1;
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end_pos.points[0].abs() + end_pos.points[1].abs()
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}
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fn main() {
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let input = parse_input(&read_input());
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println!("Part 1: {}", part1(&input));
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println!("Part 2: {}", part2(&input));
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use aoc2020::*;
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use paste::paste;
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use test::black_box;
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const TEST_INPUT: &str = "F10
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N3
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F7
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R90
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F11";
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test!(part1() == 25);
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test!(part2() == 286);
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bench!(part1() == 1838);
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bench!(part2() == 89936);
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bench_input!(len == 786);
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}
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