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use std::io::BufReader;
use std::io::BufRead;
use std::fs::File;
use std::collections::HashMap;
struct Map {
walls: Vec<Vec<bool>>,
destinations: Vec<(usize, usize)>,
start: (usize, usize)
}
impl Map {
fn new(input: &[String]) -> Map {
let mut walls = Vec::with_capacity(input.len());
let mut start = (0, 0);
let mut destinations = Vec::new();
let mut y = 0;
for line in input {
let mut x = 0;
let mut wall_row = Vec::with_capacity(line.len());
for c in line.chars() {
wall_row.push(c == '#');
if c == '0' {
start = (y, x);
}
else if c.is_numeric() {
destinations.push((y, x));
}
x += 1;
}
walls.push(wall_row);
y += 1;
}
Map {
walls: walls,
destinations: destinations,
start: start
}
}
fn is_valid_position(&self, y: i32, x: i32) -> bool {
y > 0 &&
x > 0 &&
(y as usize) < self.walls.len() &&
(x as usize) < self.walls[y as usize].len() &&
!self.walls[y as usize][x as usize]
}
}
#[derive(Clone, Hash, PartialEq, Eq)]
struct State {
robot_location: (usize, usize),
destinations_hit: Vec<bool>
}
impl State {
fn new(map: &Map) -> State {
State {
robot_location: map.start,
destinations_hit: map.destinations.iter().map(|_| false).collect()
}
}
fn next_state(&self, movement: (i32, i32), map: &Map) -> Option<State> {
let (y, x) = self.robot_location;
let (dy, dx) = movement;
let y2 = y as i32 + dy;
let x2 = x as i32 + dx;
if !map.is_valid_position(y2, x2) {
return None;
}
let y2 = y2 as usize;
let x2 = x2 as usize;
Some(State {
robot_location: (y2, x2),
destinations_hit: self.destinations_hit.iter()
.zip(map.destinations.iter())
.map(|(&hit, &(dest_y, dest_x))| hit || (dest_y == y2 && dest_x == x2))
.collect()
})
}
fn next_states(&self, map: &Map) -> Vec<State> {
[(-1, 0), (1, 0), (0, -1), (0, 1)].iter()
.filter_map(|&movement| self.next_state(movement, &map))
.collect()
}
fn is_complete(&self, map: &Map) -> bool {
self.destinations_hit.iter().all(|&x| x) && self.robot_location == map.start
}
}
fn main() {
let map = Map::new(&read_file());
let initial = State::new(&map);
let mut states = HashMap::new();
states.insert(initial, 0);
let mut moves = 0;
while !states.iter().any(|(&ref s, _)| s.is_complete(&map)) {
let new_states = states.iter()
.filter(|&(_, &m)| m == moves)
.flat_map(|(&ref s, _)| s.next_states(&map))
.collect::<Vec<_>>();
moves += 1;
for state in new_states {
if !states.contains_key(&state) {
states.insert(state, moves);
}
}
}
println!("Final state found in {} moves", moves);
}
fn read_file() -> Vec<String> {
let file = BufReader::new(File::open("input.txt").unwrap());
file.lines()
.map(|line| line.unwrap())
.filter(|line| line.len() > 0)
.collect()
}
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