77 lines
1.7 KiB
Rust
77 lines
1.7 KiB
Rust
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use std::collections::HashSet;
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use color_eyre::eyre;
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use eyre::eyre;
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use crate::lib::Vec2;
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struct Octopi {
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grid: Vec2<u8>,
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flashed: HashSet<(usize, usize)>,
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}
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impl Octopi {
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fn step(&mut self) -> usize {
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for row in 0..self.grid.row_count() {
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for col in 0..self.grid.col_count() {
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self.inc(row, col);
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}
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}
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let count = self.flashed.len();
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self.flashed.clear();
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count
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}
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fn inc(&mut self, row: usize, col: usize) {
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if self.flashed.contains(&(row, col)) {
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return;
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}
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let energy = self.grid.get_mut(row, col);
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*energy += 1;
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if *energy > 9 {
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self.flashed.insert((row, col));
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*energy = 0;
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for (n_row, n_col) in self.grid.neighbor_coords(row, col) {
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self.inc(n_row, n_col);
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}
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}
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}
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}
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fn load(data: &str) -> eyre::Result<Octopi> {
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let mut grid = Vec2::new(10);
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for line in data.lines() {
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let mut row = Vec::with_capacity(10); // kinda inefficient but whatever, it only happens once
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for c in line.chars() {
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match c.to_digit(10) {
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Some(d) => row.push(d as u8),
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None => return Err(eyre!("Invalid digit: {}", c)),
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}
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}
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grid.push(row);
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}
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Ok(Octopi {grid, flashed: HashSet::new()})
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}
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pub fn run(data: &str) -> eyre::Result<(usize, usize)> {
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let mut octopi = load(data)?;
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let mut num_flashes = 0;
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let mut two = None;
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for i in 0.. {
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let n = octopi.step();
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if i < 100 {
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num_flashes += n;
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}
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if n == 100 {
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two = Some(i);
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break;
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}
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}
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Ok((num_flashes, two.unwrap() + 1))
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}
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