104 lines
2.7 KiB
Rust
104 lines
2.7 KiB
Rust
use std::collections::{BTreeSet, VecDeque};
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use aoc_runner_derive::{aoc, aoc_generator};
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pub struct Data(Vec<Vec<u8>>);
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impl Data {
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fn shape(&self) -> (usize, usize) {
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if !self.0.iter().all(|v| v.len() == self.0[0].len()) {
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panic!("Not rectangular!");
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}
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(self.0.len(), self.0[0].len())
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}
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fn get(&self, x: i64, y: i64) -> Option<u8> {
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if x < 0 || y < 0 {
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return None;
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}
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self.0
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.get(x as usize)
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.map(|v| v.get(y as usize).copied())
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.flatten()
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}
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}
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#[aoc_generator(day09)]
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pub fn input_generator(input: &str) -> Data {
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Data(
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input
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.lines()
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.map(|l| {
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l.chars()
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.map(|c| c.to_digit(10).unwrap().try_into().unwrap())
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.collect()
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})
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.collect(),
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)
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}
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fn get_low_points(input: &Data) -> Vec<(i64, i64, u8)> {
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let mut ret = vec![];
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let (sx, sy) = input.shape();
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let sx = sx as i64;
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let sy = sy as i64;
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for x in 0..sx {
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for y in 0..sy {
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let c = input.get(x, y);
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if c.is_none() {
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continue;
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}
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let c = c.unwrap();
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let low_point = input
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.get(x + 1, y)
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.iter()
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.chain(input.get(x - 1, y).iter())
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.chain(input.get(x, y + 1).iter())
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.chain(input.get(x, y - 1).iter())
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.all(|v| v > &c);
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if low_point {
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ret.push((x, y, c))
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}
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}
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}
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ret
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}
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#[aoc(day09, part1)] // 468
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pub fn solve_part1(input: &Data) -> usize {
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get_low_points(input)
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.iter()
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.map(|(_, _, v)| (*v as usize) + 1)
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.sum()
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}
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#[aoc(day09, part2)]
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pub fn solve_part2(input: &Data) -> usize {
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let mut basins: BTreeSet<usize> = BTreeSet::new();
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let mut q = VecDeque::new();
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let mut visited = BTreeSet::<(i64, i64)>::new();
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for (x, y, c) in &get_low_points(input) {
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visited.clear();
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q.clear();
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q.push_back((*x, *y, *c));
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while let Some((x, y, c)) = q.pop_front() {
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if c == 9 || !visited.insert((x, y)) {
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continue;
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}
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for d in [-1, 1] {
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if let Some(v) = input.get(x + d, y) {
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if v > c {
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q.push_back((x + d, y, v));
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}
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}
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if let Some(v) = input.get(x, y + d) {
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if v > c {
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q.push_back((x, y + d, v));
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}
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}
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}
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}
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basins.insert(visited.len());
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}
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return basins.iter().rev().take(3).product();
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}
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