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use advent_lib::prelude::*;
#[derive(Debug,Clone,Eq,PartialEq)]
enum Cell {
Empty,
East,
South,
}
fn main() -> Result<()> {
let mut args = std::env::args();
if args.len() != 2 {
eprintln!("Usage: advent input");
}
let _ = args.next();
let filename = args.next().unwrap();
let input = advent_lib::read_lines_file(&filename)?;
let mut initial_grid = Vec::new();
for line in &input {
let mut row = Vec::new();
for c in line.chars() {
row.push(match c {
'.' => Cell::Empty,
'>' => Cell::East,
'v' => Cell::South,
_ => panic!("Unrecognized character."),
});
}
initial_grid.push(row);
}
let mut i = 0;
let mut grid = initial_grid.clone();
loop {
i += 1;
let (anything_moved, new_grid) = iterate(&grid);
grid = new_grid;
println!("iteration {}", i);
debug_grid(&grid);
if !anything_moved {
break;
}
}
println!("{}", i);
Ok(())
}
fn iterate(grid: &Vec<Vec<Cell>>) -> (bool, Vec<Vec<Cell>>) {
let mut anything_moved = false;
let height = grid.len();
let width = grid[0].len();
let mut new_grid = Vec::new();
for _ in 0 .. height {
let mut row = Vec::new();
for _ in 0 .. width {
row.push(Cell::Empty);
}
new_grid.push(row);
}
for y in 0 .. height {
for x in 0 .. width {
if grid[y][x] == Cell::East {
let new_x = (x + 1) % width;
if grid[y][new_x] == Cell::Empty {
new_grid[y][new_x] = Cell::East;
anything_moved = true;
} else {
new_grid[y][x] = Cell::East;
}
}
}
}
for y in 0 .. height {
for x in 0 .. width {
if grid[y][x] == Cell::South {
let new_y = (y + 1) % height;
if new_grid[new_y][x] == Cell::Empty
&& grid[new_y][x] != Cell::South
{
new_grid[new_y][x] = Cell::South;
anything_moved = true;
} else {
new_grid[y][x] = Cell::South;
}
}
}
}
(anything_moved, new_grid)
}
#[allow(dead_code)]
fn debug_grid(grid: &Vec<Vec<Cell>>) {
for row in grid {
for cell in row {
match cell {
Cell::Empty => print!("."),
Cell::East => print!(">"),
Cell::South => print!("v"),
}
}
println!("");
}
println!("");
}
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