2019: day10: part 1

aoc2019/benches/bench.rs

@@ -9,6 +9,7 @@ use aoc2019::day06;
 use aoc2019::day07;
 use aoc2019::day08;
 use aoc2019::day09;
+use aoc2019::day10;
 
 fn aoc2019_all(c: &mut Criterion) {
     c.bench_function("day01", |b| b.iter(|| day01::run().unwrap()));
@@ -20,6 +21,7 @@ fn aoc2019_all(c: &mut Criterion) {
     c.bench_function("day07", |b| b.iter(|| day07::run().unwrap()));
     c.bench_function("day08", |b| b.iter(|| day08::run().unwrap()));
     c.bench_function("day09", |b| b.iter(|| day09::run().unwrap()));
+    c.bench_function("day10", |b| b.iter(|| day10::run().unwrap()));
 }
 
 criterion_group! {

aoc2019/input/day10.txt

@@ -0,0 +1,20 @@
+.###.###.###.#####.#
+#####.##.###..###..#
+.#...####.###.######
+######.###.####.####
+#####..###..########
+#.##.###########.#.#
+##.###.######..#.#.#
+.#.##.###.#.####.###
+##..#.#.##.#########
+###.#######.###..##.
+###.###.##.##..####.
+.##.####.##########.
+#######.##.###.#####
+#####.##..####.#####
+##.#.#####.##.#.#..#
+###########.#######.
+#.##..#####.#####..#
+#####..#####.###.###
+####.#.############.
+####.#.#.##########.

aoc2019/src/day10.rs

@@ -0,0 +1,174 @@
+use std::collections::HashSet;
+use std::fmt::Write;
+
+use aoc::err;
+use aoc::Result;
+
+const INPUT: &str = include_str!("../input/day10.txt");
+
+pub fn run() -> Result<String> {
+    let mut res = String::with_capacity(128);
+
+    writeln!(res, "part 1: {}", part1(INPUT)?)?;
+
+    Ok(res)
+}
+
+#[derive(Debug, PartialEq, Eq, Hash)]
+struct Position {
+    x: i64,
+    y: i64,
+}
+
+#[derive(Debug, PartialEq)]
+struct Asteroid {
+    pos: Position,
+}
+
+fn gcd(a: i64, b: i64) -> i64 {
+    if b == 0 {
+        a
+    } else {
+        gcd(b, a % b)
+    }
+}
+
+fn part1(input: &str) -> Result<usize> {
+    let mut asteroids = Vec::new();
+    for (i, line) in input.lines().enumerate() {
+        for (j, c) in line.chars().enumerate() {
+            if c == '#' {
+                asteroids.push(Asteroid {
+                    pos: Position {
+                        x: j as i64,
+                        y: i as i64,
+                    },
+                })
+            }
+        }
+    }
+
+    let mut best = None;
+    for a in asteroids.iter() {
+        let mut set = HashSet::new();
+
+        for b in asteroids.iter() {
+            if a == b {
+                continue;
+            }
+
+            let direction = Position {
+                x: b.pos.x - a.pos.x,
+                y: b.pos.y - a.pos.y,
+            };
+
+            let mut div = gcd(direction.x, direction.y);
+            if div < 0 {
+                div *= -1;
+            }
+
+            set.insert(Position {
+                x: direction.x / div,
+                y: direction.y / div,
+            });
+        }
+
+        best = match best {
+            None => Some(set),
+            Some(old) => {
+                if set.len() > old.len() {
+                    Some(set)
+                } else {
+                    Some(old)
+                }
+            }
+        };
+    }
+
+    let best = best.ok_or_else(|| err!("zero asteroid provided"))?;
+    Ok(best.len())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const PROVIDED1: &str = ".#..#
+.....
+#####
+....#
+...##
+";
+
+    const PROVIDED2: &str = "......#.#.
+#..#.#....
+..#######.
+.#.#.###..
+.#..#.....
+..#....#.#
+#..#....#.
+.##.#..###
+##...#..#.
+.#....####
+";
+
+    const PROVIDED3: &str = "#.#...#.#.
+.###....#.
+.#....#...
+##.#.#.#.#
+....#.#.#.
+.##..###.#
+..#...##..
+..##....##
+......#...
+.####.###.
+";
+
+    const PROVIDED4: &str = ".#..#..###
+####.###.#
+....###.#.
+..###.##.#
+##.##.#.#.
+....###..#
+..#.#..#.#
+#..#.#.###
+.##...##.#
+.....#.#..
+";
+
+    const PROVIDED5: &str = ".#..##.###...#######
+##.############..##.
+.#.######.########.#
+.###.#######.####.#.
+#####.##.#.##.###.##
+..#####..#.#########
+####################
+#.####....###.#.#.##
+##.#################
+#####.##.###..####..
+..######..##.#######
+####.##.####...##..#
+.#####..#.######.###
+##...#.##########...
+#.##########.#######
+.####.#.###.###.#.##
+....##.##.###..#####
+.#.#.###########.###
+#.#.#.#####.####.###
+###.##.####.##.#..##
+";
+
+    #[test]
+    fn part1_provided() {
+        assert_eq!(part1(PROVIDED1).unwrap(), 8);
+        assert_eq!(part1(PROVIDED2).unwrap(), 33);
+        assert_eq!(part1(PROVIDED3).unwrap(), 35);
+        assert_eq!(part1(PROVIDED4).unwrap(), 41);
+        assert_eq!(part1(PROVIDED5).unwrap(), 210);
+    }
+
+    #[test]
+    fn part1_real() {
+        assert_eq!(part1(INPUT).unwrap(), 214);
+    }
+}

aoc2019/src/lib.rs

@@ -9,3 +9,4 @@ pub mod day06;
 pub mod day07;
 pub mod day08;
 pub mod day09;
+pub mod day10;

aoc2019/src/main.rs

@@ -10,6 +10,7 @@ use aoc2019::day06;
 use aoc2019::day07;
 use aoc2019::day08;
 use aoc2019::day09;
+use aoc2019::day10;
 
 fn main() -> Result<()> {
     let days: &[DayFunc] = &[
@@ -22,6 +23,7 @@ fn main() -> Result<()> {
         day07::run,
         day08::run,
         day09::run,
+        day10::run,
     ];
 
     aoc::run(days)