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