90 lines
2.5 KiB
Rust
90 lines
2.5 KiB
Rust
#![feature(test)]
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extern crate test;
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use std::collections::HashSet;
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use aoc2021::common::*;
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const DAY: usize = 9;
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type Parsed = Vec<Vec<u8>>;
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fn parse_input(raw: &str) -> Parsed {
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raw.lines().map(|l| l.bytes().map(|b| b - b'0').collect()).collect()
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}
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fn part1(parsed: &Parsed) -> usize {
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find_lows(parsed).into_iter().map(|(x, y)| parsed[x][y] as usize + 1).sum()
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}
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fn find_lows(parsed: &Parsed) -> Vec<(usize, usize)> {
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(0..parsed.len())
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.flat_map(|x| (0..parsed[x].len()).map(move |y| (x, y)))
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.filter(|&(x, y)| {
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// There’s gotta be some incomplete_windows or similar that makes this not as horrible
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let cur = parsed[x][y];
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all_neighbors(x, y).into_iter().filter_map(|(x, y)| parsed.get(x).and_then(|ys| ys.get(y))).all(|&n| n > cur)
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})
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.collect()
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}
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fn all_neighbors(x: usize, y: usize) -> Vec<(usize, usize)> {
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[x.checked_add(1).map(|x| (x, y)), x.checked_sub(1).map(|x| (x, y)), y.checked_add(1).map(|y| (x, y)), y.checked_sub(1).map(|y| (x, y))]
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.into_iter()
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.flatten()
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.collect()
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}
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fn grow_basin(parsed: &Parsed, points_in_basin: &mut HashSet<(usize, usize)>, (x, y): (usize, usize)) -> bool {
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let cur = parsed[x][y];
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let mut new_points = Vec::new();
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for (x, y) in all_neighbors(x, y).into_iter().filter(|p| !points_in_basin.contains(p)) {
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if parsed.get(x).and_then(|ys| ys.get(y)).unwrap_or(&0) > &cur {
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new_points.push((x, y));
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}
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}
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if new_points.iter().any(|&p| grow_basin(parsed, points_in_basin, p)) {
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points_in_basin.insert((x, y));
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true
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} else {
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false
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}
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}
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fn part2(parsed: &Parsed) -> usize {
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let lows = find_lows(parsed);
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let mut basins = Vec::new();
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for (x, y) in lows {
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let mut points_in_basin = HashSet::new();
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grow_basin(parsed, &mut points_in_basin, (x, y));
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basins.push(points_in_basin);
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}
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basins.sort_unstable_by_key(HashSet::len);
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basins.reverse();
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println!("{basins:?}");
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// basins.iter().take(3).map(|b| b.len()).product();
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unimplemented!()
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}
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fn main() {
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let input = parse_input(&read_file(DAY));
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println!("Part 1: {}", part1(&input));
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println!("Part 2: {}", part2(&input));
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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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const TEST_INPUT: &str = "2199943210
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3987894921
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9856789892
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8767896789
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9899965678";
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test!(part1() == 15);
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// test!(part2() == 1134);
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bench!(part1() == 478);
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// bench!(part2() == 0);
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bench_input!(Vec::len => 100);
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}
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