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use std::collections::HashMap;
fn main() {
let input = advent::read_lines(11);
println!("11a: {}", count_flashes(&input, 100));
println!("11b: {}", all_flashing(&input));
}
#[derive(PartialEq,Eq,Hash,Copy,Clone)]
struct Position {
x: isize,
y: isize,
}
#[derive(Clone)]
struct OctopusCavern {
grid: HashMap<Position,i8>,
flashes: usize,
}
impl OctopusCavern {
fn new<T: AsRef<str>>(input: &[T]) -> OctopusCavern {
let mut grid = HashMap::new();
for (y, line) in input.iter().enumerate() {
for (x, c) in line.as_ref().split_terminator("").skip(1).enumerate() {
let level = c.parse::<i8>().unwrap();
grid.insert(Position { x: x as isize, y: y as isize }, level);
}
}
OctopusCavern { grid, flashes: 0 }
}
fn increment_levels(&mut self) {
for (_, level) in self.grid.iter_mut() {
*level += 1;
}
}
fn can_flash(&self) -> bool {
self.grid.values().any(|&level| level > 9)
}
fn flash(&mut self) {
let mut new_grid = self.grid.clone();
for pos in self.grid.iter().filter(|(_,&level)| level > 9).map(|(&pos,_)| pos) {
self.flashes += 1;
new_grid.insert(pos, -1);
for x in -1 ..= 1 {
for y in -1 ..= 1 {
if (x, y) == (0, 0) {
continue
}
if let Some(level) = new_grid.get_mut(&Position { x: pos.x + x, y: pos.y + y }) {
if *level != -1 {
*level += 1;
}
}
}
}
}
self.grid = new_grid;
}
fn reset_levels(&mut self) {
for level in self.grid.values_mut() {
if *level == -1 {
*level = 0;
}
}
}
fn step(&mut self) {
assert!(!self.can_flash());
self.increment_levels();
while self.can_flash() {
self.flash();
}
self.reset_levels();
}
fn all_flashing(&self) -> bool {
!self.grid.values().any(|&level| level > 0)
}
}
fn count_flashes<T: AsRef<str>>(input: &[T], steps: usize) -> usize {
let mut cavern = OctopusCavern::new(input);
for _ in 0 .. steps {
cavern.step();
}
cavern.flashes
}
fn all_flashing<T: AsRef<str>>(input: &[T]) -> usize {
let mut cavern = OctopusCavern::new(input);
let mut step = 0;
loop {
step += 1;
cavern.step();
if cavern.all_flashing() {
return step;
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test0() {
let input = [
"11111",
"19991",
"19191",
"19991",
"11111",
];
assert_eq!(count_flashes(&input, 2), 9);
}
#[test]
fn test1() {
let input = [
"5483143223",
"2745854711",
"5264556173",
"6141336146",
"6357385478",
"4167524645",
"2176841721",
"6882881134",
"4846848554",
"5283751526",
];
assert_eq!(count_flashes(&input, 100), 1656);
assert_eq!(all_flashing(&input), 195);
}
}
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