use std::io::{self, BufRead}; use std::collections::VecDeque; struct Vec2D { data: Vec, xlen: usize, ylen: usize, } impl Vec2D:: { fn new(xlen: usize, ylen: usize, t: T ) -> Vec2D:: { let vec2_d = Vec2D::{ data: vec![t.clone(); xlen * ylen], xlen, ylen }; return vec2_d; } } impl Vec2D:: { fn at_mut(&mut self, x: usize, y: usize) -> Option<&mut T> { if y < self.ylen && x < self.xlen { return Some(&mut self.data[x + y * self.xlen]) } else { return None } } fn at(&self, x: usize, y: usize) -> Option<&T> { if y < self.ylen && x < self.xlen { return Some(&self.data[x + y * self.xlen]) } else { return None } } } impl std::fmt::Display for Vec2D:: where T: std::fmt::Display { fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { for y in 0..self.ylen { for x in 0..self.xlen { let _ = write!(f, "{}", *self.at(x, y).unwrap()); } let _ = writeln!(f, ""); } writeln!(f, "") } } // const UP: u8 = 0b00001000; // const DOWN: u8 = 0b00000100; // const RIGHT: u8 = 0b00000010; // const LEFT: u8 = 0b00000001; const UP: u8 = 0; const DOWN: u8 = 1; const RIGHT: u8 = 2; const LEFT: u8 = 3; #[derive(Clone, Copy)] struct Node { heat_loss: u8, min_heat_loss: u32, steps_from: [u8; 4], // direction_from: u8, // steps_from: u8, updated: bool, // if false, skip when queued } impl Node { fn new() -> Node { return Node{heat_loss: 0, min_heat_loss: u32::MAX, steps_from: [0; 4], updated: true, } } } impl std::fmt::Display for Node { fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { write!(f, "[l={}, ml={:04}{}]", self.heat_loss, self.min_heat_loss, match self.direction_from { // UP => '^', DOWN => 'v', LEFT => '<', RIGHT => '>', _ => 'X'}) UP => 'v', DOWN => '^', LEFT => '>', RIGHT => '<', _ => 'X'}) } } fn go_direction(x: usize, y: usize, x_max: usize, y_max: usize, direction: u8) -> Option<(usize, usize)> { match direction { DOWN => if y < y_max - 1 { return Some((x, y + 1)) }, UP => if y > 0 { return Some((x, y - 1)) }, RIGHT => if x < x_max - 1 { return Some((x + 1, y)) }, LEFT => if x > 0 { return Some((x - 1, y)) }, _ => panic!("Invalid direction: '{}'", direction) } None } fn traverse_grapgh(graph: &mut Vec2D::) -> u32 { let mut queue: VecDeque<(usize, usize)> = VecDeque::from([(0, 0)]); let xlen= graph.xlen; let ylen = graph.ylen; while !queue.is_empty() { let (x, y) = queue.pop_front().unwrap(); let opposite: u8; let node = *graph.at(x ,y).unwrap(); // copy required because we borrow from graph later :( if !node.updated { continue; } // update surrounding reachable nodes if they can be reached at a lower cost // dont check the one from where we came from // if updated, queue them if node.direction_from & (UP | DOWN) != 0 { opposite = node.direction_from ^ (UP | DOWN) } else { opposite = node.direction_from ^ (LEFT | RIGHT) } let mut update_direction = |direction: u8| { if direction == opposite { return } // dont update the direction from which this node was reached let mut steps: u8 = 1; if node.direction_from == direction { if node.steps_from >= 3 { return } // unreachable, because we cant walk more than 3 blocks in one direction steps += node.steps_from; } if let Some((other_x, other_y)) = go_direction(x, y, xlen, ylen, direction) { let other_node = graph.at_mut(other_x, other_y).unwrap(); let heat_loss = node.min_heat_loss + other_node.heat_loss as u32; // TODO use array if other_node.min_heat_loss > heat_loss { // update all other_node.min_heat_loss = node.min_heat_loss + other_node.heat_loss as u32; other_node.direction_from = direction; other_node.steps_from = steps; other_node.updated = true; queue.push_back((other_x, other_y)); } else if other_node.min_heat_loss == heat_loss { // mark additional possible direction other_node.min_heat_loss = node.min_heat_loss + other_node.heat_loss as u32; other_node.direction_from = direction; other_node.steps_from = steps; other_node.updated = true; queue.push_back((other_x, other_y)); } } }; update_direction(UP); update_direction(DOWN); update_direction(LEFT); update_direction(RIGHT); graph.at_mut(x ,y).unwrap().updated = false; } let min_heat_loss = graph.at(xlen - 1, ylen - 1).unwrap().min_heat_loss; return min_heat_loss; } fn main() { // let input = "input.txt"; let input = "example.txt"; // let input = "example2.txt"; let mut lines = read_lines(&input); let line_length = lines.next().expect("No line").unwrap().len(); let n_lines = lines.count() + 1; // already consumed one lines = read_lines(&input); let mut city_blocks = Vec2D::::new(line_length, n_lines, Node::new()); for (y, line) in lines.map(|r| r.ok().unwrap()).enumerate() { for (x, c) in line.as_bytes().iter().enumerate() { city_blocks.at_mut(x, y).unwrap().heat_loss = c - b'0'; } } city_blocks.at_mut(0, 0).unwrap().min_heat_loss = 0; println!("{}", city_blocks); let min_heat_loss = traverse_grapgh(&mut city_blocks); println!("{}", city_blocks); println!("Minimum heat loss: (1): {}", min_heat_loss); // let reset = |c: &mut Vec2D| c.data.iter_mut().for_each(|v| *v &= !DIRECTION) ; // // it is very stupid at no real need to optimize at this speed // for y in 0..contraption.ylen { // n_tiles = n_tiles.max(travel_beam(&mut contraption, (0, y, RIGHT))); // reset(&mut contraption); // n_tiles = n_tiles.max(travel_beam(&mut contraption, (line_length - 1, y, LEFT))); // reset(&mut contraption); // } // for x in 0..contraption.xlen { // n_tiles = n_tiles.max(travel_beam(&mut contraption, (x, 0, DOWN))); // reset(&mut contraption); // n_tiles = n_tiles.max(travel_beam(&mut contraption, (x, n_lines - 1, UP))); // reset(&mut contraption); // } // println!("Max beamed tiles: (2): {}", n_tiles); } fn read_lines

(filename: P) -> io::Lines> where P: AsRef, { return match std::fs::File::open(filename) { Err(why) => panic!("Could not open file. {}", why), Ok(file) => std::io::BufReader::new(file).lines() }; }