96 lines
2.6 KiB
Rust
96 lines
2.6 KiB
Rust
#![feature(test)]
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extern crate test;
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use std::ops::RangeInclusive;
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type TargetArea = (RangeInclusive<isize>, RangeInclusive<isize>);
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type Probe = ((isize, isize), (isize, isize));
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#[derive(Debug, PartialEq)]
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enum ProbeStatus {
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Hit,
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Miss,
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NoLongerReachable,
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}
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#[inline]
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fn calc_status(((xvel, _), (x, y)): &Probe, (xtarget, ytarget): &TargetArea) -> ProbeStatus {
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if xtarget.contains(x) && ytarget.contains(y) {
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ProbeStatus::Hit
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} else if y < ytarget.start() || x > xtarget.end() || (xvel == &0 && !xtarget.contains(x)) {
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ProbeStatus::NoLongerReachable
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} else {
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ProbeStatus::Miss
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}
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}
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#[inline]
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fn step(((xvel, yvel), (x, y)): &Probe) -> Probe {
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((xvel - xvel.signum(), yvel - 1), (x + xvel, y + yvel))
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}
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fn get_target() -> TargetArea {
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(34..=67, -215..=-186)
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}
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fn part1(hits: &[isize]) -> isize {
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(1..=*hits.iter().max().unwrap()).sum()
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}
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fn find_hits(target: &TargetArea) -> Vec<isize> {
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// Doing y in the outer loop and x in the inner would allow us to call last() instead of max()
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// in part1, however, for reasons unknown to me, that makes this function 20% slower.
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(1..=*target.0.end())
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.flat_map(move |x| (*target.1.start()..-target.1.start()).map(move |y| (x, y)))
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.filter_map(|(startx, starty)| {
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let mut probe = ((startx, starty), (0, 0));
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loop {
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probe = step(&probe);
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match calc_status(&probe, target) {
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ProbeStatus::Hit => return Some(starty),
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ProbeStatus::Miss => continue,
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ProbeStatus::NoLongerReachable => return None,
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}
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}
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})
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.collect()
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}
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fn main() {
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let hits = find_hits(&get_target());
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println!("Part 1: {}", part1(&hits));
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println!("Part 2: {}", hits.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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use aoc2021::*;
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#[test]
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fn part1_test() {
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let input = (20..=30, -10..=-5);
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let hits = find_hits(&input);
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assert_eq!(part1(&hits), 45);
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}
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#[test]
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fn part2_test() {
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let input = (20..=30, -10..=-5);
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let hits = find_hits(&input);
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assert_eq!(hits.len(), 112);
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}
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#[bench]
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fn bench_find_hits(b: &mut test::Bencher) {
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let input = get_target();
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b.iter(|| assert_eq!(find_hits(test::black_box(&input)).len(), 2040))
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}
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#[bench]
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fn bench_part1(b: &mut test::Bencher) {
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let input = get_target();
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let hits = find_hits(&input);
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b.iter(|| assert_eq!(part1(test::black_box(&hits)), 23005))
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}
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}
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