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More day 17 optimizations

This commit is contained in:
kageru 2021-12-17 17:32:35 +01:00
parent 36ffc1cf00
commit 66bc3c6d42
Signed by: kageru
GPG Key ID: 8282A2BEA4ADA3D2
1 changed files with 15 additions and 19 deletions
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34
2021/src/bin/day17.rs
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@ -1,7 +1,6 @@
#![feature(core_intrinsics)]
#![feature(test)] #![feature(test)]
extern crate test; extern crate test;
use std::{intrinsics::unlikely, ops::RangeInclusive}; use std::ops::RangeInclusive;
type TargetArea = (RangeInclusive<isize>, RangeInclusive<isize>); type TargetArea = (RangeInclusive<isize>, RangeInclusive<isize>);
type Probe = ((isize, isize), (isize, isize)); type Probe = ((isize, isize), (isize, isize));
@ -29,27 +28,25 @@ fn step(((xvel, yvel), (x, y)): &Probe) -> Probe {
((xvel - xvel.signum(), yvel - 1), (x + xvel, y + yvel)) ((xvel - xvel.signum(), yvel - 1), (x + xvel, y + yvel))
} }
fn parse_input() -> TargetArea { fn get_target() -> TargetArea {
(34..=67, -215..=-186) (34..=67, -215..=-186)
} }
fn part1(hits: &[((isize, isize), isize)]) -> isize { fn part1(hits: &[isize]) -> isize {
*hits.iter().map(|(_, y)| y).max().unwrap() (1..=*hits.iter().max().unwrap()).sum()
} }
fn find_hits(target: &TargetArea) -> Vec<((isize, isize), isize)> { fn find_hits(target: &TargetArea) -> Vec<isize> {
// Doing y in the outer loop and x in the inner would allow us to call last() instead of max()
// in part1, however, for reasons unknown to me, that makes this function 20% slower.
(1..=*target.0.end()) (1..=*target.0.end())
.flat_map(move |x| (*target.1.start()..250).map(move |y| (x, y))) .flat_map(move |x| (*target.1.start()..250).map(move |y| (x, y)))
.filter_map(|start| { .filter_map(|(startx, starty)| {
let mut probe = (start, (0, 0)); let mut probe = ((startx, starty), (0, 0));
let mut y_high = 0;
loop { loop {
probe = step(&probe); probe = step(&probe);
if unlikely(probe.0 .1 == 0) {
y_high = probe.1 .1;
}
match calc_status(&probe, target) { match calc_status(&probe, target) {
ProbeStatus::Hit => return Some((start, y_high)), ProbeStatus::Hit => return Some(starty),
ProbeStatus::Miss => continue, ProbeStatus::Miss => continue,
ProbeStatus::NoLongerReachable => return None, ProbeStatus::NoLongerReachable => return None,
} }
@ -59,8 +56,7 @@ fn find_hits(target: &TargetArea) -> Vec<((isize, isize), isize)> {
} }
fn main() { fn main() {
let target = parse_input(); let hits = find_hits(&get_target());
let hits = find_hits(&target);
println!("Part 1: {}", part1(&hits)); println!("Part 1: {}", part1(&hits));
println!("Part 2: {}", hits.len()); println!("Part 2: {}", hits.len());
} }
@ -86,14 +82,14 @@ mod tests {
#[bench] #[bench]
fn bench_find_hits(b: &mut test::Bencher) { fn bench_find_hits(b: &mut test::Bencher) {
let input = parse_input(); let input = get_target();
b.iter(|| assert_eq!(find_hits(&input).len(), 2040)) b.iter(|| assert_eq!(find_hits(test::black_box(&input)).len(), 2040))
} }
#[bench] #[bench]
fn bench_part1(b: &mut test::Bencher) { fn bench_part1(b: &mut test::Bencher) {
let input = parse_input(); let input = get_target();
let hits = find_hits(&input); let hits = find_hits(&input);
b.iter(|| assert_eq!(part1(&hits), 23005)) b.iter(|| assert_eq!(part1(test::black_box(&hits)), 23005))
} }
} }