mirror of
https://github.com/bertptrs/adventofcode.git
synced 2025-12-25 21:00:31 +01:00
Bert Peters
e0e1bc26e8
The second part doesn't actually need to start the search at the low points; just iterating everything and keeping track of visited spaces is enough. Now that the iterator is only used in part 1, we inline the iterator to remove some overhead from the code.
120 lines
2.8 KiB
Rust
120 lines
2.8 KiB
Rust
use std::cmp::Reverse;
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use std::io::Read;
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pub fn part1(input: &mut dyn Read) -> String {
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let mut buffer = Vec::new();
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input.read_to_end(&mut buffer).unwrap();
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let lines: Vec<_> = buffer
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.split(|&s| s == b'\n')
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.filter(|s| !s.is_empty())
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.collect();
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let mut total_danger = 0;
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for y in 0..lines.len() {
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for x in 0..lines[y].len() {
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if x > 0 && lines[y][x - 1] <= lines[y][x] {
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continue;
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}
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if x + 1 < lines[y].len() && lines[y][x + 1] <= lines[y][x] {
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continue;
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}
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if y > 0 && lines[y - 1][x] <= lines[y][x] {
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continue;
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}
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if y + 1 < lines.len() && lines[y + 1][x] <= lines[y][x] {
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continue;
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}
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total_danger += 1 + (lines[y][x] - b'0') as i32;
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}
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}
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total_danger.to_string()
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}
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pub fn part2(input: &mut dyn Read) -> String {
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let mut buffer = Vec::new();
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input.read_to_end(&mut buffer).unwrap();
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let mut visited_buffer = vec![false; buffer.len()];
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let lines: Vec<_> = buffer
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.split(|&s| s == b'\n')
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.filter(|s| !s.is_empty())
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.collect();
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let mut visited: Vec<_> = visited_buffer.chunks_exact_mut(lines[0].len()).collect();
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let mut todo = Vec::new();
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let mut sizes = Vec::with_capacity(4);
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for y in 0..lines.len() {
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for x in 0..lines[0].len() {
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if visited[y][x] || lines[y][x] == b'9' {
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continue;
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}
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todo.push((x, y));
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let mut size = 1;
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visited[y][x] = true;
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while let Some((x, y)) = todo.pop() {
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let mut add = |x: usize, y: usize| {
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if lines[y][x] != b'9' && !visited[y][x] {
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size += 1;
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visited[y][x] = true;
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todo.push((x, y));
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}
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};
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if x > 0 {
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add(x - 1, y);
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}
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if x + 1 < lines[y].len() {
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add(x + 1, y);
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}
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if y > 0 {
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add(x, y - 1)
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}
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if y + 1 < lines.len() {
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add(x, y + 1);
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}
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}
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sizes.push(Reverse(size));
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sizes.sort_unstable();
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sizes.truncate(3);
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}
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}
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sizes.into_iter().fold(1, |a, Reverse(b)| a * b).to_string()
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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 crate::test_implementation;
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const SAMPLE: &[u8] = include_bytes!("samples/09.txt");
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#[test]
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fn sample_part1() {
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test_implementation(part1, SAMPLE, 15);
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}
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#[test]
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fn sample_part2() {
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test_implementation(part2, SAMPLE, 1134);
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}
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}
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