2019: day03: 100x speedup
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parent
989fc854d9
commit
3a6e9d58b6
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@ -1,5 +1,4 @@
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use std::collections::HashMap;
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use std::collections::HashSet;
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use std::cmp::{max, min};
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use std::error::Error;
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use std::fmt::Write;
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use std::str::FromStr;
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@ -12,7 +11,7 @@ const INPUT: &str = include_str!("../input/day03.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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let (first, second) = parse_paths(INPUT)?;
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let (first, second) = parse_wires(INPUT)?;
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writeln!(res, "part 1: {}", part1(&first, &second)?)?;
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writeln!(res, "part 2: {}", part2(&first, &second)?)?;
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@ -20,11 +19,178 @@ pub fn run() -> Result<String> {
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Ok(res)
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}
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enum Move {
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Up(i64),
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Down(i64),
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Left(i64),
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Right(i64),
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fn manhattan_distance(a: &Point, b: &Point) -> u64 {
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(a.x - b.x).abs() as u64 + (a.y - b.y).abs() as u64
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}
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fn part1(first_wire: &Wire, second_wire: &Wire) -> Result<u64> {
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first_wire
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.0
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.iter()
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.flat_map(|first_seg| {
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second_wire
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.0
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.iter()
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.map(move |second_seg| (first_seg, second_seg))
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})
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.filter_map(|(f, s)| match f.intersection(s) {
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Some(Point { x: 0, y: 0 }) | None => None,
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Some(p) => Some(p),
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})
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.map(|inter| manhattan_distance(&inter, &Point { x: 0, y: 0 }))
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.min()
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.ok_or_else(|| err!("wire was empty"))
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}
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fn part2(first_wire: &Wire, second_wire: &Wire) -> Result<u64> {
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let mut min_dist = None;
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let mut first_length = 0;
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for seg1 in first_wire.0.iter() {
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let mut second_length = 0;
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for seg2 in second_wire.0.iter() {
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if let Some(inter) = seg1.intersection(&seg2) {
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if inter.x == 0 && inter.y == 0 {
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continue;
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}
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let path_length = first_length
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+ second_length
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+ manhattan_distance(&inter, &seg1.begin)
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+ manhattan_distance(&inter, &seg2.begin);
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min_dist = match min_dist {
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Some(dist) => Some(min(dist, path_length)),
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None => Some(path_length),
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};
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}
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second_length += manhattan_distance(&seg2.begin, &seg2.end);
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}
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first_length += manhattan_distance(&seg1.begin, &seg1.end);
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}
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min_dist.ok_or_else(|| err!("wire was empty"))
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}
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fn parse_wires(input: &str) -> Result<(Wire, Wire)> {
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let mut lines = input.lines();
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let first = lines
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.next()
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.ok_or_else(|| err!("input missing a line"))?
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.parse()?;
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let second = lines
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.next()
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.ok_or_else(|| err!("input missing a line"))?
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.parse()?;
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Ok((first, second))
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}
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#[derive(Debug)]
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struct Wire(Vec<Segment>);
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impl FromStr for Wire {
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type Err = Box<dyn Error>;
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fn from_str(s: &str) -> Result<Wire> {
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let moves = s
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.trim_end()
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.split(',')
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.map(|m| m.parse())
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.collect::<Result<Vec<Move>>>()
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.map_err(|e| err!("failed to parse wire: {}", e))?;
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let mut pos = Point { x: 0, y: 0 };
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let mut wire = Vec::with_capacity(moves.len());
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for mv in moves {
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let mut new_pos = pos;
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match mv.direction {
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Direction::Up => {
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new_pos.y += mv.length;
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}
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Direction::Down => {
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new_pos.y -= mv.length;
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}
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Direction::Left => {
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new_pos.x -= mv.length;
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}
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Direction::Right => {
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new_pos.x += mv.length;
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}
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}
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wire.push(Segment {
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begin: pos,
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end: new_pos,
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min_x: min(pos.x, new_pos.x),
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max_x: max(pos.x, new_pos.x),
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min_y: min(pos.y, new_pos.y),
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max_y: max(pos.y, new_pos.y),
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});
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pos = new_pos;
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}
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Ok(Wire(wire))
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}
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}
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#[derive(Clone, Copy, Debug)]
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struct Point {
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x: i64,
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y: i64,
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}
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#[derive(Debug)]
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struct Segment {
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begin: Point,
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end: Point,
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min_x: i64,
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max_x: i64,
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min_y: i64,
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max_y: i64,
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}
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impl Segment {
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fn intersection(&self, other: &Segment) -> Option<Point> {
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if self.min_x >= other.min_x
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&& self.min_x <= other.max_x
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&& other.min_y >= self.min_y
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&& other.min_y <= self.max_y
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{
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Some(Point {
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x: self.min_x,
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y: other.min_y,
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})
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} else if other.min_x >= self.min_x
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&& other.min_x <= self.max_x
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&& self.min_y >= other.min_y
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&& self.min_y <= other.max_y
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{
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Some(Point {
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x: other.min_x,
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y: self.min_y,
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})
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} else {
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None
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}
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}
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}
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enum Direction {
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Up,
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Down,
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Left,
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Right,
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}
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struct Move {
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direction: Direction,
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length: i64,
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}
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impl FromStr for Move {
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@ -42,107 +208,18 @@ impl FromStr for Move {
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let length = s.parse()?;
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match direction {
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'U' => Ok(Move::Up(length)),
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'D' => Ok(Move::Down(length)),
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'L' => Ok(Move::Left(length)),
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'R' => Ok(Move::Right(length)),
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_ => Err(err!("couldn't parse direction: {}", direction)),
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}
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let direction = match direction {
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'U' => Direction::Up,
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'D' => Direction::Down,
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'L' => Direction::Left,
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'R' => Direction::Right,
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_ => return Err(err!("couldn't parse direction: {}", direction)),
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};
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Ok(Move { direction, length })
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}
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}
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fn path_count(mut a: (i64, i64), b: (i64, i64), mut start_count: u64) -> Vec<((i64, i64), u64)> {
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let mut res = Vec::new();
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while a != b {
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if a.0 < b.0 {
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a.0 += 1;
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} else if a.0 > b.0 {
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a.0 -= 1;
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}
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if a.1 < b.1 {
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a.1 += 1;
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} else if a.1 > b.1 {
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a.1 -= 1;
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}
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start_count += 1;
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res.push((a, start_count));
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}
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res
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}
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fn parse_path_with_count(line: &str) -> Result<HashMap<(i64, i64), u64>> {
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let moves = line
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.trim_end()
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.split(',')
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.map(|m| m.parse())
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.collect::<Result<Vec<Move>>>()?;
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let mut pos = (0, 0);
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let mut count = 0;
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Ok(moves
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.iter()
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.flat_map(|mv| {
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let new_pos = match mv {
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Move::Up(dy) => (pos.0, pos.1 - dy),
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Move::Down(dy) => (pos.0, pos.1 + dy),
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Move::Left(dx) => (pos.0 - dx, pos.1),
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Move::Right(dx) => (pos.0 + dx, pos.1),
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};
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let p = path_count(pos, new_pos, count);
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count += manhattan_distance(pos, new_pos);
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pos = new_pos;
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p
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})
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.collect())
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}
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fn parse_paths(input: &str) -> Result<(HashMap<(i64, i64), u64>, HashMap<(i64, i64), u64>)> {
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let mut lines = input.lines();
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let first_path =
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parse_path_with_count(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
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let second_path =
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parse_path_with_count(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
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Ok((first_path, second_path))
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}
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fn manhattan_distance(a: (i64, i64), b: (i64, i64)) -> u64 {
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(a.0 - b.0).abs() as u64 + (a.1 - b.1).abs() as u64
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}
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fn part1(
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first_path: &HashMap<(i64, i64), u64>,
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second_path: &HashMap<(i64, i64), u64>,
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) -> Result<u64> {
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let first_path = first_path.keys().collect::<HashSet<_>>();
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let second_path = second_path.keys().collect::<HashSet<_>>();
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let cross_locations = first_path.intersection(&second_path);
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cross_locations
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.map(|(x, y)| manhattan_distance((*x, *y), (0, 0)))
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.min()
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.ok_or_else(|| err!("the cables never crossed !"))
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}
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fn part2(
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first_path: &HashMap<(i64, i64), u64>,
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second_path: &HashMap<(i64, i64), u64>,
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) -> Result<u64> {
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first_path
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.keys()
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.filter(|pos| second_path.contains_key(&pos))
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.map(|pos| first_path.get(&pos).unwrap() + second_path.get(&pos).unwrap())
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.min()
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.ok_or_else(|| err!("cables never crossed !"))
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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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@ -161,33 +238,33 @@ U98,R91,D20,R16,D67,R40,U7,R15,U6,R7
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#[test]
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fn part1_provided() {
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let (first, second) = parse_paths(PROVIDED1).unwrap();
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let (first, second) = parse_wires(PROVIDED1).unwrap();
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assert_eq!(part1(&first, &second).unwrap(), 6);
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let (first, second) = parse_paths(PROVIDED2).unwrap();
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let (first, second) = parse_wires(PROVIDED2).unwrap();
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assert_eq!(part1(&first, &second).unwrap(), 159);
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let (first, second) = parse_paths(PROVIDED3).unwrap();
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let (first, second) = parse_wires(PROVIDED3).unwrap();
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assert_eq!(part1(&first, &second).unwrap(), 135);
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}
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#[test]
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fn part1_real() {
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let (first, second) = parse_paths(INPUT).unwrap();
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let (first, second) = parse_wires(INPUT).unwrap();
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assert_eq!(part1(&first, &second).unwrap(), 273);
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}
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#[test]
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fn part2_provided() {
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let (first, second) = parse_paths(PROVIDED1).unwrap();
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let (first, second) = parse_wires(PROVIDED1).unwrap();
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assert_eq!(part2(&first, &second).unwrap(), 30);
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let (first, second) = parse_paths(PROVIDED2).unwrap();
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let (first, second) = parse_wires(PROVIDED2).unwrap();
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assert_eq!(part2(&first, &second).unwrap(), 610);
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let (first, second) = parse_paths(PROVIDED3).unwrap();
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let (first, second) = parse_wires(PROVIDED3).unwrap();
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assert_eq!(part2(&first, &second).unwrap(), 410);
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}
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#[test]
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fn part2_real() {
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let (first, second) = parse_paths(INPUT).unwrap();
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let (first, second) = parse_wires(INPUT).unwrap();
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assert_eq!(part2(&first, &second).unwrap(), 15622);
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}
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}
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