wip

17/day17.rs

@@ -0,0 +1,188 @@
+use std::io::{self, BufRead};
+use std::collections::VecDeque;
+
+struct Vec2D<T> {
+    data: Vec<T>,
+    xlen: usize,
+    ylen: usize,
+}
+
+impl<T: std::clone::Clone> Vec2D::<T> {
+    fn new(xlen: usize, ylen: usize, t: T ) -> Vec2D::<T> {
+        let vec2_d = Vec2D::<T>{ data: vec![t.clone(); xlen * ylen], xlen, ylen };
+        return vec2_d;
+    }
+}
+impl<T> Vec2D::<T> {
+    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<T> std::fmt::Display for Vec2D::<T>
+    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::<Node>) -> 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::<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(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<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);
+}
+
+fn read_lines<P>(filename: P) -> io::Lines<io::BufReader<std::fs::File>>
+where P: AsRef<std::path::Path>, {
+    return match std::fs::File::open(filename) {
+        Err(why) => panic!("Could not open file. {}", why),
+        Ok(file) => std::io::BufReader::new(file).lines()
+    };
+}
+