Add day8

2024/day8/.gitignore

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+target
+input.txt

2024/day8/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day8"
+version = "0.1.0"
+dependencies = [
+ "gcd",
+]
+
+[[package]]
+name = "gcd"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d758ba1b47b00caf47f24925c0074ecb20d6dfcffe7f6d53395c0465674841a"

2024/day8/Cargo.toml

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+[package]
+name = "day8"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+gcd = "2.3.0"

2024/day8/src/main.rs

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+use std::{
+    collections::{HashMap, HashSet},
+    fs,
+    time::Instant,
+};
+
+use gcd::Gcd;
+
+fn main() {
+    let file = fs::read_to_string("./input.txt").unwrap();
+
+    let mut map = Vec::new();
+    let mut antenna_locations: HashMap<char, Vec<Point>> = HashMap::new();
+
+    for (r_idx, line) in file.lines().enumerate() {
+        map.push(line.as_bytes());
+
+        for (c_idx, ch) in line.chars().enumerate() {
+            if ch != '.' {
+                antenna_locations
+                    .entry(ch)
+                    .or_default()
+                    .push(Point::new(r_idx as i32, c_idx as i32));
+            }
+        }
+    }
+
+    let start = Instant::now();
+    println!("Solution 1: {}", puzzle1(&map, &antenna_locations));
+    let end = Instant::now() - start;
+    println!("Solution 1 time: {}", end.as_micros());
+
+    let start = Instant::now();
+    println!("Solution 2: {}", puzzle2(&map, &antenna_locations));
+    let end = Instant::now() - start;
+    println!("Solution 2 time: {}", end.as_micros());
+}
+
+#[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
+struct Point {
+    row: i32,
+    col: i32,
+}
+
+impl Point {
+    fn new(row: i32, col: i32) -> Self {
+        Self { row, col }
+    }
+
+    fn is_in_map(&self, map: &[&[u8]]) -> bool {
+        !(self.col >= map[0].len() as i32
+            || self.row >= map.len() as i32
+            || self.col < 0
+            || self.row < 0)
+    }
+}
+
+fn puzzle1(map: &[&[u8]], antenna_locations: &HashMap<char, Vec<Point>>) -> i32 {
+    let mut antinodes = HashSet::new();
+
+    for (_, loc) in antenna_locations.iter() {
+        for i in 0..loc.len() {
+            for j in (i + 1)..loc.len() {
+                let diff = Point::new(loc[i].row - loc[j].row, loc[i].col - loc[j].col);
+                let an1 = Point::new(loc[i].row + diff.row, loc[i].col + diff.col);
+                let an2 = Point::new(loc[j].row - diff.row, loc[j].col - diff.col);
+
+                if an1.is_in_map(map) {
+                    antinodes.insert(an1);
+                }
+                if an2.is_in_map(map) {
+                    antinodes.insert(an2);
+                }
+            }
+        }
+    }
+
+    antinodes.len() as i32
+}
+
+fn puzzle2(map: &[&[u8]], antenna_locations: &HashMap<char, Vec<Point>>) -> i32 {
+    let mut antinodes = HashSet::new();
+
+    for (_, loc) in antenna_locations.iter() {
+        for i in 0..loc.len() {
+            for j in (i + 1)..loc.len() {
+                let mut diff = Point::new(loc[i].row - loc[j].row, loc[i].col - loc[j].col);
+                let gcd = diff.row.unsigned_abs().gcd_binary(diff.col.unsigned_abs()) as i32;
+                diff.row /= gcd;
+                diff.col /= gcd;
+
+                let mut add = true;
+                let mut n = 0;
+
+                while add {
+                    add = false;
+                    let an1 = Point::new(loc[i].row + n * diff.row, loc[i].col + n * diff.col);
+                    let an2 = Point::new(loc[j].row - n * diff.row, loc[j].col - n * diff.col);
+
+                    if an1.is_in_map(map) {
+                        antinodes.insert(an1);
+                        add = true;
+                    }
+                    if an2.is_in_map(map) {
+                        antinodes.insert(an2);
+                        add = true;
+                    }
+                    n += 1;
+                }
+            }
+        }
+    }
+
+    antinodes.len() as i32
+}