100 lines
2.7 KiB
Rust
100 lines
2.7 KiB
Rust
use aoc_runner_derive::{aoc, aoc_generator};
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use grid::Grid;
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use itertools::Itertools;
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use rustc_hash::FxHashSet;
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use std::io::BufRead;
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type HashSet<T> = FxHashSet<T>;
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#[aoc_generator(day8)]
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pub fn get_input(input: &[u8]) -> AntennaMap {
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AntennaMap::from(input)
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}
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pub struct AntennaMap {
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map: Grid<u8>,
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}
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impl<T: BufRead> From<T> for AntennaMap {
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fn from(input: T) -> Self {
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Self { map: Grid::from(input) }
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}
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}
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impl AntennaMap {
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fn find_antinodes(&self, start: usize, reps: Option<usize>) -> Grid<bool> {
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let mut antinodes = Grid::with_shape(self.map.width(), self.map.height(), false);
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// find the unique frequencies in a dumb way
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// NOTE: The dumb way is faster than the slightly-smarter ways I tried
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let freq_set: HashSet<&u8> = HashSet::from_iter(self.map.data.iter().filter(|c| **c != b'.'));
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// for each unique frequency, get all the pairs' positions
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for freq in freq_set {
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for pair in self
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.map
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.data
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.iter()
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.enumerate()
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.filter(|(_, c)| *c == freq)
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.map(|(i, _)| self.map.coord(i as i64).unwrap())
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.permutations(2)
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{
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// permutations generates both pairs, ie. ((1,2),(2,1)) and ((2,1),(1,2)) so we don't need
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// to consider the 'negative' side of the line, which will be generated by the other pair
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let (a, b) = (pair[0], pair[1]);
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let offset = (a.0 - b.0, a.1 - b.1);
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for i in (start..).map_while(|i| if Some(i - start) != reps { Some(i as i64) } else { None }) {
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let node_pos = (a.0 + i * offset.0, a.1 + i * offset.1);
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if antinodes.set(&node_pos, true).is_none() {
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// left the grid
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break;
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}
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}
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}
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}
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antinodes
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}
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}
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// PROBLEM 1 solution
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#[aoc(day8, part1)]
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pub fn part1(map: &AntennaMap) -> u64 {
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let antinodes = map.find_antinodes(1, Some(1));
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antinodes.count(&true) as u64
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}
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// PROBLEM 2 solution
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#[aoc(day8, part2)]
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pub fn part2(map: &AntennaMap) -> u64 {
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let antinodes = map.find_antinodes(0, None);
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antinodes.count(&true) as u64
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}
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#[cfg(test)]
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mod tests {
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use crate::day8::*;
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const EXAMPLE: &[u8] = b"............
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........0...
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.....0......
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.......0....
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....0.......
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......A.....
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............
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............
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........A...
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.........A..
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............
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............";
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#[test]
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fn part1_example() {
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assert_eq!(part1(&get_input(EXAMPLE)), 14);
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}
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#[test]
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fn part2_example() {
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assert_eq!(part2(&get_input(EXAMPLE)), 34);
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}
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}
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