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https://github.com/bertptrs/adventofcode.git
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108 lines
2.5 KiB
Rust
108 lines
2.5 KiB
Rust
use std::io::Read;
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fn read_grid<'a>(input: &'_ mut dyn Read, buffer: &'a mut Vec<u8>) -> Vec<&'a mut [u8]> {
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input.read_to_end(buffer).unwrap();
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let mut grid: Vec<&mut [u8]> = buffer.split_mut(|&b| b == b'\n').collect();
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grid.iter_mut()
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.flat_map(|line| line.iter_mut())
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.for_each(|b| *b -= b'0');
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grid
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}
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fn advance(grid: &mut [&mut [u8]], todo: &mut Vec<(i8, i8)>) -> usize {
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let mut flashes = 0;
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grid.iter_mut()
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.enumerate()
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.flat_map(|(y, line)| {
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line.iter_mut()
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.enumerate()
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.map(move |(x, value)| (x, y, value))
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})
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.for_each(|(x, y, value)| {
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*value += 1;
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if *value > 9 {
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todo.push((x as i8, y as i8));
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}
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});
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while let Some((x, y)) = todo.pop() {
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flashes += 1;
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for dy in -1..=1 {
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for dx in -1..=1 {
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if dx == 0 && dy == 0 {
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continue;
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}
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let nx = usize::try_from(x + dx);
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let ny = usize::try_from(y + dy);
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if let (Ok(nx), Ok(ny)) = (nx, ny) {
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if let Some(value) = grid.get_mut(ny).and_then(|line| line.get_mut(nx)) {
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*value += 1;
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if *value == 10 {
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todo.push((nx as i8, ny as i8));
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}
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}
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}
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}
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}
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}
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grid.iter_mut()
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.flat_map(|line| line.iter_mut())
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.filter(|b| **b > 9)
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.for_each(|b| *b = 0);
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flashes
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}
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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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let mut grid = read_grid(input, &mut buffer);
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let mut todo = Vec::new();
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(0..100)
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.map(|_| advance(&mut grid, &mut todo))
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.sum::<usize>()
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.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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let mut grid = read_grid(input, &mut buffer);
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let mut todo = Vec::new();
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let target: usize = grid.iter().map(|line| line.len()).sum();
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(1..)
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.find(|_| advance(&mut grid, &mut todo) == target)
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.unwrap()
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.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/11.txt");
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#[test]
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fn sample_part1() {
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test_implementation(part1, SAMPLE, 1656);
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}
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#[test]
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fn sample_part2() {
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test_implementation(part2, SAMPLE, 195);
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}
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}
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