86 lines
2.3 KiB
Rust
86 lines
2.3 KiB
Rust
#![feature(test)]
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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, Position2D { x: 0, y: 0 }), |(dir, pos), (cmd, dist)| match cmd {
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'N' => (dir, pos + Position2D::from((0, *dist))),
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'S' => (dir, pos - Position2D::from((0, *dist))),
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'E' => (dir, pos + Position2D::from((*dist, 0))),
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'W' => (dir, pos - Position2D::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 + Position2D::from(dir) * *dist),
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_ => unreachable!(),
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})
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.1;
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end_pos.x.abs() + end_pos.y.abs()
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}
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fn rotate_waypoint(mut wp: Position2D, deg: i64) -> Position2D {
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for _ in 0..((deg / 90 + 4) % 4) {
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wp = Position2D { x: wp.y, y: -wp.x };
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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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(Position2D { x: 10, y: 1 }, Position2D { x: 0, y: 0 }),
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|(wp, pos), (cmd, dist)| match cmd {
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'N' => (wp + Position2D::from((0, *dist)), pos),
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'S' => (wp - Position2D::from((0, *dist)), pos),
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'E' => (wp + Position2D::from((*dist, 0)), pos),
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'W' => (wp - Position2D::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.x.abs() + end_pos.y.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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