Day 11 (easy)

main
Inga 🏳‍🌈 4 years ago
parent 47fb1fcdd8
commit f777a09f63
  1. 10
      day11/Cargo.toml
  2. 193
      day11/src/main.rs

@ -0,0 +1,10 @@
[package]
name = "day11"
version = "0.1.0"
authors = ["inga-lovinde <52715130+inga-lovinde@users.noreply.github.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
ndarray = "0.14.0"

@ -0,0 +1,193 @@
#![feature(trait_alias)]
use std::io::{self, BufRead};
use ndarray::Array2;
// state (u32 for simplicity reasons): 0/1/2/3 (in this case, 1 = floor, 2 = seat free, 3 = seat taken)
// every cell is u32, where:
// * lowest 16 bits describe its neighbours:
// * bits 0-1 (cell & 3) is the state of upper left neighbour,
// * bits 2-3 ((cell >> 2) & 3) is the state of upper neighbour,
// * bits 4-5 is the state of upper right neighbour,
// * bits 6-7, left,
// * bits 8-9, right,
// * bits 10-11, bottom left,
// * bits 12-13, bottom,
// * bits 14-15, bottom right
// * bits 16-17 ((cell >> 16) & 3) describe the cell itself
// rule: cell (u32, 18 bits used) -> new cell (u32)
// board is indexed by [row, column],
// where row is from top to bottom and column is from left to right
trait StateRules = Fn([usize; 4], u32) -> u32;
struct Game {
cell_rules: Vec<u32>,
board: Array2<u32>,
rows: usize,
columns: usize,
}
impl Game {
// only updates the state of this cell for it and its neighbours;
// only state of this cell is used from new_cell
fn update_cell(&mut self, row: usize, column: usize, new_cell: u32) {
let state_diff = (new_cell ^ self.board[[row, column]]) >> 16;
self.board[[row, column]] ^= state_diff << 16;
self.board[[row+1, column+1]] ^= state_diff;
self.board[[row+1, column ]] ^= state_diff << 2;
self.board[[row+1, column-1]] ^= state_diff << 4;
self.board[[row , column+1]] ^= state_diff << 6;
self.board[[row , column-1]] ^= state_diff << 8;
self.board[[row-1, column+1]] ^= state_diff << 10;
self.board[[row-1, column ]] ^= state_diff << 12;
self.board[[row-1, column-1]] ^= state_diff << 14;
}
fn build_cell_rules<T: StateRules>(state_rules: T) -> Vec<u32> {
let mut result = vec![0u32; 1 << 18];
for i in 0..1usize << 18 {
let cell = i as u32;
let current_state = (cell >> 16) & 3;
let mut state_counts = [0usize; 4];
for j in 0..8 {
state_counts[((cell >> (2*j)) & 3) as usize] += 1;
}
let new_state = state_rules(state_counts, current_state);
let new_cell = cell ^ ((current_state ^ new_state) << 16);
result[i] = new_cell;
}
result
}
pub fn next_step(&mut self) -> usize {
let mut changes: Vec<_> = vec![];
for row in 1..self.rows-1 {
for column in 1..self.columns-1 {
let old_cell = self.board[[row, column]];
let new_cell = self.cell_rules[old_cell as usize];
if new_cell != old_cell {
changes.push((row, column, new_cell));
}
}
}
let changes_count = changes.len();
for (row, column, new_cell) in changes {
self.update_cell(row, column, new_cell);
}
changes_count
}
pub fn from_input<T: StateRules>(input_data: &[String], state_rules: T) -> Game {
let rows = input_data.len() + 2;
let columns = input_data[0].len() + 2;
let mut states = Array2::zeros((rows, columns));
for row in 1..rows-1 {
let chars = input_data[row-1].chars().collect::<Vec<_>>();
for column in 1..columns-1 {
let ch = chars[column-1];
states[[row, column]] = match ch {
'.' => 1,
'L' => 2,
'#' => 3,
_ => 0,
}
}
}
let mut board = Array2::zeros((rows, columns));
/*
board[[0, 0]] = states[[1, 1]] << 14;
board[[0, columns-1]] = states[[1, columns-2]] << 10;
board[[rows-1, 0]] = states[[rows-2, 1]] << 4;
board[[rows-1, columns-1]] = states[[rows-2, columns-2]];
for row in 1..rows-1 {
board[[row, 0]] = (states[[row-1, 1]] << 4) ^ (states[[row, 1]] << 8) ^ (states[[row+1, 1]] << 14);
board[[row, columns-1]] = (states[[row-1, columns-2]]) ^ (states[[row, columns-2]] << 6) ^ (states[[row+1, columns-2]] << 10);
}
for column in 1..columns-1 {
board[[0, column]] = (states[[1, column-1]] << 10) ^ (states[[1, column]] << 12) ^ (states[[1, column+1]] << 14);
board[[rows-1, column]] = (states[[rows-2, column-1]]) ^ (states[[rows-2, column]] << 2) ^ (states[[rows-2, column+1]] << 4);
}
*/
for row in 1..rows-1 {
for column in 1..columns-1 {
board[[row, column]] =
(states[[row-1, column-1]] ) ^
(states[[row-1, column ]] << 2) ^
(states[[row-1, column+1]] << 4) ^
(states[[row , column-1]] << 6) ^
(states[[row , column+1]] << 8) ^
(states[[row+1, column-1]] << 10) ^
(states[[row+1, column ]] << 12) ^
(states[[row+1, column+1]] << 14) ^
(states[[row, column]] << 16);
}
}
let cell_rules = Self::build_cell_rules(state_rules);
Game {
rows,
columns,
board,
cell_rules,
}
}
pub fn print_board(&self) {
for row in (&self.board).genrows() {
println!("{}", row.iter().map(|state| {
match (state >> 16) & 3 {
1 => '.',
2 => 'L',
3 => '#',
_ => '0',
}
}).collect::<String>());
}
}
pub fn get_count_of_cells_for_state(&self, state: u32) -> usize {
(&self.board).iter().filter(|&&cell| ((cell >> 16) & 3) == state).count()
}
}
fn main() {
let stdin = io::stdin();
let lines: Vec<_> = stdin.lock().lines().map(|line| line.unwrap()).collect();
let mut game = Game::from_input(&lines, |state_counts: [usize; 4], current_state| {
match current_state {
2 => if state_counts[3] == 0 { 3 } else { 2 },
3 => if state_counts[3] >= 4 { 2 } else { 3 },
other => other
}
});
for i in 1.. {
let changes_count = game.next_step();
println!("Iteration {}; changed cells: {}", i, changes_count);
if changes_count == 0 {
break;
}
}
println!("Board stabilized at {} occupied seats", game.get_count_of_cells_for_state(3));
game.print_board();
println!("Board stabilized at {} occupied seats", game.get_count_of_cells_for_state(3));
}
Loading…
Cancel
Save