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