2019: day03: 100x speedup

This commit is contained in:
Antoine Martin 2019-12-07 00:29:42 +01:00
parent 989fc854d9
commit 3a6e9d58b6

View file

@ -1,5 +1,4 @@
use std::collections::HashMap; use std::cmp::{max, min};
use std::collections::HashSet;
use std::error::Error; use std::error::Error;
use std::fmt::Write; use std::fmt::Write;
use std::str::FromStr; use std::str::FromStr;
@ -12,7 +11,7 @@ const INPUT: &str = include_str!("../input/day03.txt");
pub fn run() -> Result<String> { pub fn run() -> Result<String> {
let mut res = String::with_capacity(128); let mut res = String::with_capacity(128);
let (first, second) = parse_paths(INPUT)?; let (first, second) = parse_wires(INPUT)?;
writeln!(res, "part 1: {}", part1(&first, &second)?)?; writeln!(res, "part 1: {}", part1(&first, &second)?)?;
writeln!(res, "part 2: {}", part2(&first, &second)?)?; writeln!(res, "part 2: {}", part2(&first, &second)?)?;
@ -20,11 +19,178 @@ pub fn run() -> Result<String> {
Ok(res) Ok(res)
} }
enum Move { fn manhattan_distance(a: &Point, b: &Point) -> u64 {
Up(i64), (a.x - b.x).abs() as u64 + (a.y - b.y).abs() as u64
Down(i64), }
Left(i64),
Right(i64), fn part1(first_wire: &Wire, second_wire: &Wire) -> Result<u64> {
first_wire
.0
.iter()
.flat_map(|first_seg| {
second_wire
.0
.iter()
.map(move |second_seg| (first_seg, second_seg))
})
.filter_map(|(f, s)| match f.intersection(s) {
Some(Point { x: 0, y: 0 }) | None => None,
Some(p) => Some(p),
})
.map(|inter| manhattan_distance(&inter, &Point { x: 0, y: 0 }))
.min()
.ok_or_else(|| err!("wire was empty"))
}
fn part2(first_wire: &Wire, second_wire: &Wire) -> Result<u64> {
let mut min_dist = None;
let mut first_length = 0;
for seg1 in first_wire.0.iter() {
let mut second_length = 0;
for seg2 in second_wire.0.iter() {
if let Some(inter) = seg1.intersection(&seg2) {
if inter.x == 0 && inter.y == 0 {
continue;
}
let path_length = first_length
+ second_length
+ manhattan_distance(&inter, &seg1.begin)
+ manhattan_distance(&inter, &seg2.begin);
min_dist = match min_dist {
Some(dist) => Some(min(dist, path_length)),
None => Some(path_length),
};
}
second_length += manhattan_distance(&seg2.begin, &seg2.end);
}
first_length += manhattan_distance(&seg1.begin, &seg1.end);
}
min_dist.ok_or_else(|| err!("wire was empty"))
}
fn parse_wires(input: &str) -> Result<(Wire, Wire)> {
let mut lines = input.lines();
let first = lines
.next()
.ok_or_else(|| err!("input missing a line"))?
.parse()?;
let second = lines
.next()
.ok_or_else(|| err!("input missing a line"))?
.parse()?;
Ok((first, second))
}
#[derive(Debug)]
struct Wire(Vec<Segment>);
impl FromStr for Wire {
type Err = Box<dyn Error>;
fn from_str(s: &str) -> Result<Wire> {
let moves = s
.trim_end()
.split(',')
.map(|m| m.parse())
.collect::<Result<Vec<Move>>>()
.map_err(|e| err!("failed to parse wire: {}", e))?;
let mut pos = Point { x: 0, y: 0 };
let mut wire = Vec::with_capacity(moves.len());
for mv in moves {
let mut new_pos = pos;
match mv.direction {
Direction::Up => {
new_pos.y += mv.length;
}
Direction::Down => {
new_pos.y -= mv.length;
}
Direction::Left => {
new_pos.x -= mv.length;
}
Direction::Right => {
new_pos.x += mv.length;
}
}
wire.push(Segment {
begin: pos,
end: new_pos,
min_x: min(pos.x, new_pos.x),
max_x: max(pos.x, new_pos.x),
min_y: min(pos.y, new_pos.y),
max_y: max(pos.y, new_pos.y),
});
pos = new_pos;
}
Ok(Wire(wire))
}
}
#[derive(Clone, Copy, Debug)]
struct Point {
x: i64,
y: i64,
}
#[derive(Debug)]
struct Segment {
begin: Point,
end: Point,
min_x: i64,
max_x: i64,
min_y: i64,
max_y: i64,
}
impl Segment {
fn intersection(&self, other: &Segment) -> Option<Point> {
if self.min_x >= other.min_x
&& self.min_x <= other.max_x
&& other.min_y >= self.min_y
&& other.min_y <= self.max_y
{
Some(Point {
x: self.min_x,
y: other.min_y,
})
} else if other.min_x >= self.min_x
&& other.min_x <= self.max_x
&& self.min_y >= other.min_y
&& self.min_y <= other.max_y
{
Some(Point {
x: other.min_x,
y: self.min_y,
})
} else {
None
}
}
}
enum Direction {
Up,
Down,
Left,
Right,
}
struct Move {
direction: Direction,
length: i64,
} }
impl FromStr for Move { impl FromStr for Move {
@ -42,105 +208,16 @@ impl FromStr for Move {
let length = s.parse()?; let length = s.parse()?;
match direction { let direction = match direction {
'U' => Ok(Move::Up(length)), 'U' => Direction::Up,
'D' => Ok(Move::Down(length)), 'D' => Direction::Down,
'L' => Ok(Move::Left(length)), 'L' => Direction::Left,
'R' => Ok(Move::Right(length)), 'R' => Direction::Right,
_ => Err(err!("couldn't parse direction: {}", direction)), _ => return Err(err!("couldn't parse direction: {}", direction)),
}
}
}
fn path_count(mut a: (i64, i64), b: (i64, i64), mut start_count: u64) -> Vec<((i64, i64), u64)> {
let mut res = Vec::new();
while a != b {
if a.0 < b.0 {
a.0 += 1;
} else if a.0 > b.0 {
a.0 -= 1;
}
if a.1 < b.1 {
a.1 += 1;
} else if a.1 > b.1 {
a.1 -= 1;
}
start_count += 1;
res.push((a, start_count));
}
res
}
fn parse_path_with_count(line: &str) -> Result<HashMap<(i64, i64), u64>> {
let moves = line
.trim_end()
.split(',')
.map(|m| m.parse())
.collect::<Result<Vec<Move>>>()?;
let mut pos = (0, 0);
let mut count = 0;
Ok(moves
.iter()
.flat_map(|mv| {
let new_pos = match mv {
Move::Up(dy) => (pos.0, pos.1 - dy),
Move::Down(dy) => (pos.0, pos.1 + dy),
Move::Left(dx) => (pos.0 - dx, pos.1),
Move::Right(dx) => (pos.0 + dx, pos.1),
}; };
let p = path_count(pos, new_pos, count); Ok(Move { direction, length })
count += manhattan_distance(pos, new_pos); }
pos = new_pos;
p
})
.collect())
}
fn parse_paths(input: &str) -> Result<(HashMap<(i64, i64), u64>, HashMap<(i64, i64), u64>)> {
let mut lines = input.lines();
let first_path =
parse_path_with_count(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
let second_path =
parse_path_with_count(lines.next().ok_or_else(|| err!("missing line in input"))?)?;
Ok((first_path, second_path))
}
fn manhattan_distance(a: (i64, i64), b: (i64, i64)) -> u64 {
(a.0 - b.0).abs() as u64 + (a.1 - b.1).abs() as u64
}
fn part1(
first_path: &HashMap<(i64, i64), u64>,
second_path: &HashMap<(i64, i64), u64>,
) -> Result<u64> {
let first_path = first_path.keys().collect::<HashSet<_>>();
let second_path = second_path.keys().collect::<HashSet<_>>();
let cross_locations = first_path.intersection(&second_path);
cross_locations
.map(|(x, y)| manhattan_distance((*x, *y), (0, 0)))
.min()
.ok_or_else(|| err!("the cables never crossed !"))
}
fn part2(
first_path: &HashMap<(i64, i64), u64>,
second_path: &HashMap<(i64, i64), u64>,
) -> Result<u64> {
first_path
.keys()
.filter(|pos| second_path.contains_key(&pos))
.map(|pos| first_path.get(&pos).unwrap() + second_path.get(&pos).unwrap())
.min()
.ok_or_else(|| err!("cables never crossed !"))
} }
#[cfg(test)] #[cfg(test)]
@ -161,33 +238,33 @@ U98,R91,D20,R16,D67,R40,U7,R15,U6,R7
#[test] #[test]
fn part1_provided() { fn part1_provided() {
let (first, second) = parse_paths(PROVIDED1).unwrap(); let (first, second) = parse_wires(PROVIDED1).unwrap();
assert_eq!(part1(&first, &second).unwrap(), 6); assert_eq!(part1(&first, &second).unwrap(), 6);
let (first, second) = parse_paths(PROVIDED2).unwrap(); let (first, second) = parse_wires(PROVIDED2).unwrap();
assert_eq!(part1(&first, &second).unwrap(), 159); assert_eq!(part1(&first, &second).unwrap(), 159);
let (first, second) = parse_paths(PROVIDED3).unwrap(); let (first, second) = parse_wires(PROVIDED3).unwrap();
assert_eq!(part1(&first, &second).unwrap(), 135); assert_eq!(part1(&first, &second).unwrap(), 135);
} }
#[test] #[test]
fn part1_real() { fn part1_real() {
let (first, second) = parse_paths(INPUT).unwrap(); let (first, second) = parse_wires(INPUT).unwrap();
assert_eq!(part1(&first, &second).unwrap(), 273); assert_eq!(part1(&first, &second).unwrap(), 273);
} }
#[test] #[test]
fn part2_provided() { fn part2_provided() {
let (first, second) = parse_paths(PROVIDED1).unwrap(); let (first, second) = parse_wires(PROVIDED1).unwrap();
assert_eq!(part2(&first, &second).unwrap(), 30); assert_eq!(part2(&first, &second).unwrap(), 30);
let (first, second) = parse_paths(PROVIDED2).unwrap(); let (first, second) = parse_wires(PROVIDED2).unwrap();
assert_eq!(part2(&first, &second).unwrap(), 610); assert_eq!(part2(&first, &second).unwrap(), 610);
let (first, second) = parse_paths(PROVIDED3).unwrap(); let (first, second) = parse_wires(PROVIDED3).unwrap();
assert_eq!(part2(&first, &second).unwrap(), 410); assert_eq!(part2(&first, &second).unwrap(), 410);
} }
#[test] #[test]
fn part2_real() { fn part2_real() {
let (first, second) = parse_paths(INPUT).unwrap(); let (first, second) = parse_wires(INPUT).unwrap();
assert_eq!(part2(&first, &second).unwrap(), 15622); assert_eq!(part2(&first, &second).unwrap(), 15622);
} }
} }