Solve 08

src/bin/08.rs

@@ -0,0 +1,84 @@
+use aoc::*;
+use glam::IVec2;
+use itertools::Itertools;
+use std::collections::{HashMap, HashSet};
+use std::iter;
+
+const INPUT: &str = include_str!("../../input/08");
+
+fn main() {
+    assert_example!(part1, "08-test", 14);
+    println!("Part 1: {}", part1(INPUT));
+    assert_example!(part2, "08-test", 34);
+    println!("Part 2: {}", part2(INPUT));
+}
+
+fn part1(input: &str) -> usize {
+    let (map, grid_size) = parse(input);
+    let mut antinodes = HashSet::new();
+
+    for antennas in map.values() {
+        for (&a, &b) in antennas.iter().tuple_combinations() {
+            let distance = b - a;
+            let antinode = b + distance;
+            if grid_contains(antinode, grid_size) {
+                antinodes.insert(antinode);
+            }
+            let antinode = a - distance;
+            if grid_contains(antinode, grid_size) {
+                antinodes.insert(antinode);
+            }
+        }
+    }
+
+    antinodes.len()
+}
+
+fn part2(input: &str) -> usize {
+    let (map, grid_size) = parse(input);
+    let mut antinodes = HashSet::new();
+    const RESONANCE: i32 = 50;
+
+    for antennas in map.values() {
+        for (&a, &b) in antennas.iter().tuple_combinations() {
+            let distance = b - a;
+            for r in -RESONANCE..RESONANCE {
+                let antinode = b + distance * r;
+                if grid_contains(antinode, grid_size) {
+                    antinodes.insert(antinode);
+                }
+            }
+        }
+    }
+
+    antinodes.len()
+}
+
+fn grid_contains(point: IVec2, size: IVec2) -> bool {
+    point.x >= 0 && point.y >= 0 && point.x < size.x && point.y < size.y
+}
+
+fn parse(input: &str) -> (HashMap<char, Vec<IVec2>>, IVec2) {
+    let antennas = input
+        .lines()
+        .enumerate()
+        .flat_map(|(y, line)| {
+            line.chars()
+                .enumerate()
+                .zip(iter::repeat(y))
+                .map(|((x, c), y)| (c, IVec2::new(x as i32, y as i32)))
+        })
+        .filter(|&(c, _)| c != '.');
+
+    let mut map: HashMap<char, Vec<IVec2>> = HashMap::new();
+    for (c, pos) in antennas {
+        map.entry(c).or_default().push(pos);
+    }
+
+    let size = IVec2::new(
+        input.lines().count() as i32,
+        input.lines().next().unwrap().len() as i32,
+    );
+
+    (map, size)
+}