115 lines
2.7 KiB
Rust
115 lines
2.7 KiB
Rust
use std::collections::HashSet;
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fn square(x: usize, y: usize) -> Vec<(usize, usize)> {
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let mut sq = Vec::new();
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if y > 0 {
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if x > 0 {
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sq.push((x - 1, y - 1))
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}
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sq.push((x, y - 1));
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if x < 9 {
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sq.push((x + 1, y - 1))
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}
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}
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if x > 0 {
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sq.push((x - 1, y))
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}
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if x < 9 {
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sq.push((x + 1, y))
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}
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if y < 9 {
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if x > 0 {
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sq.push((x - 1, y + 1))
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}
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sq.push((x, y + 1));
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if x < 9 {
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sq.push((x + 1, y + 1))
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}
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}
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sq
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}
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fn step(grid: &mut Vec<Vec<u32>>) -> usize {
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let mut flashed = HashSet::new();
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loop {
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let mut new_flashes = false;
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for (y, row) in grid.iter().enumerate() {
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for (x, octopus) in row.iter().enumerate() {
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let adjacent = square(x, y)
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.iter()
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.filter(|(xx, yy)| flashed.contains(&(*xx, *yy)))
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.count() as u32;
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if (octopus + adjacent + 1) >= 10 && !flashed.contains(&(x, y)) {
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flashed.insert((x, y));
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new_flashes = true;
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}
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}
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}
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if !new_flashes {
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break;
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}
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}
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for (y, row) in grid.iter_mut().enumerate() {
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for (x, octopus) in row.iter_mut().enumerate() {
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*octopus = if flashed.contains(&(x, y)) {
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0
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} else {
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*octopus
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+ square(x, y)
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.iter()
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.filter(|(xx, yy)| flashed.contains(&(*xx, *yy)))
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.count() as u32
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+ 1
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};
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}
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}
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flashed.len()
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}
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fn total_flashes(input: &str) -> usize {
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let mut octopuses = input
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.lines()
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.map(|line| {
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line.chars()
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.map(|c| char::to_digit(c, 10).unwrap())
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.collect::<Vec<u32>>()
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})
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.collect::<Vec<Vec<u32>>>();
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(0..100).fold(0, |acc, _| acc + step(&mut octopuses))
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}
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fn first_simultaneous_step(input: &str) -> usize {
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let mut octopuses = input
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.lines()
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.map(|line| {
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line.chars()
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.map(|c| char::to_digit(c, 10).unwrap())
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.collect::<Vec<u32>>()
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})
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.collect::<Vec<Vec<u32>>>();
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let mut s = 0;
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loop {
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s += 1;
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if step(&mut octopuses) == 100 {
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break;
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}
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}
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s
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}
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fn main() {
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const INPUT: &str = include_str!("../inputs/day11.txt");
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println!("solution {}", total_flashes(INPUT));
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println!("solution {}", first_simultaneous_step(INPUT));
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}
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#[test]
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fn test_square() {
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assert_eq!(square(0, 0), vec![(1, 0), (0, 1), (1, 1)]);
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}
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