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day17: rust

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matthias@arch 2023-12-18 11:37:18 +01:00
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17/README.md Normal file
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# [Day 17](https://adventofcode.com/2023/day/17)
:gift::gift::gift::gift::gift::gift::gift::gift::gift::gift::gift::gift::gift::gift::gift::gift::gift:
Today's language: **Rust**
Lines of code: **177**
Execution time: **0,429 s**
```shell
rustc day17.rs
./day17
```

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17/day17.rs
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@ -1,6 +1,7 @@
use std::io::{self, BufRead};
use std::collections::VecDeque;
#[derive(Clone)]
struct Vec2D<T> {
data: Vec<T>,
xlen: usize,
@ -37,35 +38,38 @@ impl<T> std::fmt::Display for Vec2D::<T>
}
// 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;
type Direction = u8;
const UP: Direction = 0;
const DOWN: Direction = 1;
const RIGHT: Direction = 2;
const LEFT: Direction = 3;
const OPPOSITE: [u8; 4] = [DOWN, UP, RIGHT, LEFT];
const OPPOSITE: [Direction; 4] = [DOWN, UP, LEFT, RIGHT];
const CHAR: [char; 4] = ['^', 'v', '>', '<'];
type HeatLoss = u32;
#[derive(Clone, Copy)]
struct Node {
heat_loss: u8,
min_heat_loss: u32,
heat_loss: HeatLoss,
min_heat_from: [HeatLoss; 4],
steps_from: [u8; 4],
// direction_from: u8,
// steps_from: u8,
updated: bool, // if false, skip when queued
updated_from: [bool; 4], // 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, } }
fn new() -> Node { return Node{heat_loss: 0, min_heat_from: [u32::MAX; 4], steps_from: [0; 4], updated_from: [true; 4] } }
}
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, self.steps_from[UP as usize], self.steps_from[DOWN as usize], self.steps_from[LEFT as usize], self.steps_from[RIGHT as usize])
// match self.direction_from {
// // UP => '^', DOWN => 'v', LEFT => '<', RIGHT => '>', _ => 'X'})
// UP => 'v', DOWN => '^', LEFT => '>', RIGHT => '<', _ => 'X'})
let _ = write!(f, "[l={}", self.heat_loss);
for i in 0..4 {
if self.min_heat_from[i] == u32::MAX {
let _ = write!(f, "| ");
}
else {
let _ = write!(f, "|{:03}{}", self.min_heat_from[i], CHAR[OPPOSITE[i] as usize]);
}
}
write!(f, "] ")
}
}
@ -73,76 +77,122 @@ impl std::fmt::Display for Node {
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)) },
UP => if y >= 1 { 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)) },
LEFT => if x >= 1 { return Some((x - 1, y)) },
_ => panic!("Invalid direction: '{}'", direction)
}
None
}
fn traverse_grapgh(graph: &mut Vec2D::<Node>) -> u32 {
let mut queue: VecDeque<(usize, usize)> = VecDeque::from([(0, 0)]);
type Queue = VecDeque<(usize, usize, Direction)>;
fn traverse_graph1(graph: &mut Vec2D::<Node>) -> u32 {
let mut queue: Queue = VecDeque::from([(0, 0, RIGHT), (0, 0, DOWN)]);
let xlen= graph.xlen;
let ylen = graph.ylen;
while !queue.is_empty() {
let (x, y) = queue.pop_front().unwrap();
let (x, y, direction_from) = queue.pop_front().unwrap();
let node = *graph.at(x ,y).unwrap(); // copy required because we borrow from graph later :(
if !node.updated { continue; }
if !node.updated_from[direction_from as usize] { continue; }
// update surrounding reachable nodes if they can be reached at a lower cost
// dont check the direction where we came from
// if updated, queue them
// println!("At ({},{}) from {}", x, y, CHAR[direction_from as usize]);
let mut update_direction = |direction: u8| {
if node.steps_from[OPPOSITE[direction as usize] as usize] != 0 { return } // dont update directions from which this node was reached
// check if multiple ways work
if node.steps_from.iter().filter(|c| c != 0).count() == 1 && node.steps_from[direction as usize] >= 3 { return }
if // unreachable, because we cant walk more than 3 blocks in one direction
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
let steps = node.steps_from[direction as usize]; .iter().filter(|c| **c > 0).min().unwrap_or() + 1;
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.steps_from = [0; 4];
// if this node can be reached multiple ways,
// choose the way that minimizes the other node's steps from this direction
other_node.steps_from[direction as usize] = steps;
other_node.updated = true;
queue.push_back((other_x, other_y));
let start_heat_loss = node.min_heat_from[direction_from as usize].min(node.min_heat_from[OPPOSITE[direction_from as usize] as usize]);
if direction_from == UP || direction_from == DOWN {
update_direction(&mut queue, graph, start_heat_loss, x, y, RIGHT, 3, 0);
update_direction(&mut queue, graph, start_heat_loss, x, y, LEFT, 3, 0);
}
else if other_node.min_heat_loss == heat_loss { // mark additional possible direction
// other_node.steps_from[direction as usize] = node.steps_from[direction as usize] + 1;
other_node.steps_from[direction as usize] = steps;
other_node.updated = true;
queue.push_back((other_x, other_y));
else {
update_direction(&mut queue, graph, start_heat_loss, x, y, UP, 3, 0);
update_direction(&mut queue, graph, start_heat_loss, x, y, DOWN, 3, 0);
}
}
};
update_direction(UP);
update_direction(DOWN);
update_direction(LEFT);
update_direction(RIGHT);
graph.at_mut(x ,y).unwrap().updated = false;
graph.at_mut(x ,y).unwrap().updated_from[direction_from as usize] = false;
}
let min_heat_loss = graph.at(xlen - 1, ylen - 1).unwrap().min_heat_loss;
let min_heat_loss = *graph.at(xlen - 1, ylen - 1).unwrap().min_heat_from.iter().min().unwrap();
return min_heat_loss;
}
fn traverse_graph2(graph: &mut Vec2D::<Node>) -> u32 {
let mut queue: VecDeque<(usize, usize, Direction)> = VecDeque::from([(0, 0, RIGHT), (0, 0, DOWN)]);
let xlen= graph.xlen;
let ylen = graph.ylen;
while !queue.is_empty() {
let (x, y, direction_from) = queue.pop_front().unwrap();
let node = *graph.at(x ,y).unwrap(); // copy required because we borrow from graph later :(
if !node.updated_from[direction_from as usize] { continue; }
// println!("At ({},{}) from {}", x, y, CHAR[direction_from as usize]);
let start_heat_loss = node.min_heat_from[direction_from as usize].min(node.min_heat_from[OPPOSITE[direction_from as usize] as usize]);
if direction_from == UP || direction_from == DOWN {
update_direction(&mut queue, graph, start_heat_loss, x, y, RIGHT, 7, 3);
update_direction(&mut queue, graph, start_heat_loss, x, y, LEFT, 7, 3);
}
else {
update_direction(&mut queue, graph, start_heat_loss, x, y, UP, 7, 3);
update_direction(&mut queue, graph, start_heat_loss, x, y, DOWN, 7, 3);
}
graph.at_mut(x ,y).unwrap().updated_from[direction_from as usize] = false;
}
let min_heat_loss = *graph.at(xlen - 1, ylen - 1).unwrap().min_heat_from.iter().min().unwrap();
return min_heat_loss;
}
fn update_direction(queue: &mut Queue, graph: &mut Vec2D<Node>, mut start_heat_loss: u32, mut start_x: usize, mut start_y: usize, direction: Direction, n_steps: usize, n_skip: usize) {
let xlen= graph.xlen;
let ylen = graph.ylen;
for _ in 0..n_skip {
if let Some((other_x, other_y)) = go_direction(start_x, start_y, xlen, ylen, direction) {
let other_node = graph.at_mut(other_x, other_y).unwrap();
start_heat_loss += other_node.heat_loss;
start_x = other_x;
start_y = other_y;
// println!(" {} - skipping ({},{}): {} ", CHAR[direction as usize], other_x, other_y, start_heat_loss);
}
else {
// println!(" {} - skipping out of range ", CHAR[direction as usize]);
return;
}
}
for _ in 0..n_steps {
if let Some((other_x, other_y)) = go_direction(start_x, start_y, xlen, ylen, direction) {
// print!(" {} - check ({},{}): {} ", CHAR[direction as usize], other_x, other_y, start_heat_loss);
let other_node = graph.at_mut(other_x, other_y).unwrap();
start_heat_loss += other_node.heat_loss;
if other_node.min_heat_from[direction as usize] > start_heat_loss { // update all
other_node.min_heat_from[direction as usize] = start_heat_loss;
other_node.updated_from[direction as usize] = true;
queue.push_back((other_x, other_y, direction));
// println!("+ shorter");
// dont break because we might reach a shorter node
}
// else {
// println!("X longer");
// }
start_x = other_x;
start_y = other_y;
}
else {
// println!(" {} - out of range ", CHAR[direction as usize]);
return;
}
}
}
fn main() {
// let input = "input.txt";
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
@ -150,33 +200,17 @@ fn main() {
let mut city_blocks = Vec2D::<Node>::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(x, y).unwrap().heat_loss = (c - b'0') as HeatLoss;
}
}
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);
city_blocks.at_mut(0, 0).unwrap().min_heat_from = [0; 4];
let min_heat_loss = traverse_graph1(&mut city_blocks.clone());
// println!("{}", city_blocks);
println!("Minimum heat loss: (1): {}", min_heat_loss);
// let reset = |c: &mut Vec2D<u8>| 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);
let min_heat_loss = traverse_graph2(&mut city_blocks);
// println!("{}", city_blocks);
println!("Minimum heat loss: (2): {}", min_heat_loss);
}
fn read_lines<P>(filename: P) -> io::Lines<io::BufReader<std::fs::File>>
@ -186,4 +220,3 @@ where P: AsRef<std::path::Path>, {
Ok(file) => std::io::BufReader::new(file).lines()
};
}

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README.md
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@ -19,5 +19,6 @@ This is a repository for my solutions for the [advent of code 2023](https://adve
| [14](14) | Rust | 85 | 0,172 s | no bruteforce in < 90 lines |
| [15](15) | Rust | 54 | 0,002 s | hashmap |
| [16](16) | Rust | 147 | 0,091 s | |
| [17](17) | Rust | 177 | 0,429 s | |
Lines of code are without blank lines and comments