Day 8: Resonant Collinearity
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Rust
Pretty happy with my solution today. I took my time today as it was a bit of a slow day and did it in Rust instead of python. Having proper Vec2 types is very nice.
Tap for spoiler
use std::{collections::HashMap, error::Error, io::Read};
use glam::{IVec2, Vec2};
fn permutations_of_size_two(antennas: &[Vec2]) -> Vec<[&Vec2; 2]> {
let mut permutations = vec![];
for (i, antenna) in antennas.iter().enumerate() {
for j in 0..antennas.len() {
if i == j {
continue;
}
permutations.push([antenna, &antennas[j]])
}
}
permutations
}
fn main() -> Result<(), Box<dyn Error>> {
let mut input = String::new();
std::io::stdin().read_to_string(&mut input)?;
let height = input.lines().count() as i32;
let width = input.lines().next().unwrap().len() as i32;
let antenna_positions = input
.lines()
.enumerate()
.flat_map(|(y, l)|
l.chars().enumerate().map(move |(x, c)| (Vec2::new(x as f32, y as f32), c))
)
.filter(|(_v, c)| *c != '.')
.fold(HashMap::new(), |mut acc: HashMap<char, Vec<_>> , current| {
acc.entry(current.1).or_default().push(current.0);
acc
});
let mut antinodes = vec![];
for (_c, antennas) in antenna_positions {
let perms = permutations_of_size_two(&antennas);
for [first, second] in perms {
let mut i = 1.;
loop {
let antinode = (first + (second-first) * i).round();
if (0..height).contains(&(antinode.x as i32)) &&
(0..width).contains(&(antinode.y as i32)) {
antinodes.push(antinode);
} else {
break;
}
i += 1.;
}
}
}
let mut antinode_count = 0;
let map = input
.lines()
.enumerate()
.map(|(y, l)|
l.chars().enumerate().map(|(x, c)| {
if antinodes.contains(&Vec2::new(x as f32, y as f32)) {
println!("({x},{y})");
antinode_count += 1;
return '#';
}
c
}).collect::<String>()
)
.collect::<Vec<_>>()
.join("\n");
println!("{map}");
println!("{antinode_count}");
Ok(())
}
