Day 17 part 2
This commit is contained in:
parent
5bc57e235f
commit
0c5498df01
339
src/day17.rs
339
src/day17.rs
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@ -1,12 +1,28 @@
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use std::{collections::BinaryHeap, fmt::Debug, fs::DirEntry};
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use std::{
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collections::{BinaryHeap, HashMap},
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fmt::Debug,
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fs::DirEntry,
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};
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use itertools::Itertools;
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pub fn run() {
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let input = include_str!("../input/day17.txt");
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let map: Map = input.into();
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let path = map.dijkstra_ish((0, 0), (map.width as isize - 1, map.height as isize - 1), 3);
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let path = map.dijkstra_ish(
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(0, 0),
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(map.width as isize - 1, map.height as isize - 1),
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Map::part1_edges,
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);
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dbg!(map.path_cost(&path.unwrap()));
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let path2 = map.dijkstra_ish(
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(0, 0),
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(map.width as isize - 1, map.height as isize - 1),
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Map::part2_edges,
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);
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dbg!(map.part2_path_cost(&path2.unwrap()));
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}
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#[derive(Clone)]
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@ -50,7 +66,7 @@ impl Debug for Map {
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}
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
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enum Direction {
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Up,
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Down,
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@ -96,7 +112,7 @@ struct Edge {
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direction: Direction,
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dest: (isize, isize),
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cost: u8,
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steps: u8,
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steps: usize,
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}
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impl Map {
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@ -104,11 +120,15 @@ impl Map {
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col >= 0 && col < self.width as isize && row >= 0 && row < self.height as isize
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}
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fn edges_from(&self, pos: (isize, isize), incoming_dir: Option<Direction>) -> Vec<Edge> {
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fn part1_edges(
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&self,
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pos: (isize, isize),
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incoming_dir: Option<(Direction, usize)>,
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) -> Vec<Edge> {
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Direction::all()
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.iter()
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.filter_map(|&d| {
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if incoming_dir.is_some_and(|x| x == d.opposite()) {
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if incoming_dir.is_some_and(|(x, c)| x == d.opposite() || (x == d && c >= 3)) {
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return None;
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}
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let moved = d.move_pos(pos);
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@ -125,45 +145,53 @@ impl Map {
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.collect()
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}
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// fn edges_from_ultra(
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// &self,
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// pos: (isize, isize),
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// incoming_dir: Option<(Direction, usize)>,
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// ) -> Vec<Edge> {
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// let mut v = vec![];
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// for d in Direction::all() {
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// for dist in 4..=10 {
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// let moved = d.move_pos_count(pos, dist);
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// let costs_sum = (1..=dist)
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// .map(|c| {
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// let moved = d.move_pos_count(pos, c);
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// self.costs[moved.1 as usize][moved.0 as usize]
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// })
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// .sum();
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// if self.in_bounds(moved) {
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// v.push(Edge {
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// direction: d,
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// dest: moved,
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// cost: costs_sum,
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// steps: dist as u8,
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// });
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// }
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// }
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// }
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// v
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// }
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fn part2_edges(
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&self,
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pos: (isize, isize),
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incoming_dir: Option<(Direction, usize)>,
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) -> Vec<Edge> {
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let mut v = vec![];
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for d in Direction::all() {
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if incoming_dir.is_some_and(|(x, _)| x == d.opposite()) {
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continue;
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}
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for dist in 4..=10 {
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if incoming_dir.is_some_and(|(x, c)| x == d && (c + dist) > 10) {
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continue;
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}
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let moved = d.move_pos_count(pos, dist as isize);
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if !self.in_bounds(moved) {
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continue;
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}
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let costs_sum = (1..=dist)
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.map(|c| {
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let moved = d.move_pos_count(pos, c as isize);
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self.costs[moved.1 as usize][moved.0 as usize]
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})
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.sum();
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v.push(Edge {
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direction: d,
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dest: moved,
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cost: costs_sum,
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steps: dist,
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});
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}
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}
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v
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}
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fn dijkstra_ish(
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&self,
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start: (isize, isize),
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end: (isize, isize),
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max_single_direction: usize,
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edges_fn: impl Fn(&Self, (isize, isize), Option<(Direction, usize)>) -> Vec<Edge>,
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) -> Option<Vec<(isize, isize)>> {
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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struct QueueEntry {
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neg_cost: isize,
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inbound_dir: Option<Direction>,
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inbound_dir_count: usize,
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inbound: Option<(Direction, usize)>,
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pos: (isize, isize),
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}
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impl Ord for QueueEntry {
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@ -178,92 +206,94 @@ impl Map {
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}
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let mut queue = BinaryHeap::<QueueEntry>::new();
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let mut distances = vec![vec![[[usize::MAX; 4]; 4]; self.width]; self.height];
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let mut prev = vec![vec![[[None; 4]; 4]; self.width]; self.height];
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for d in Direction::all() {
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distances[start.1 as usize][start.0 as usize][d as usize][0] = 0;
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#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
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struct HistoryKey {
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pos: (isize, isize),
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inbound: Option<(Direction, usize)>,
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}
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let mut distances = HashMap::<HistoryKey, usize>::new();
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let mut prev = HashMap::<HistoryKey, HistoryKey>::new();
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distances.insert(
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HistoryKey {
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pos: start,
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inbound: None,
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},
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0,
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);
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queue.push(QueueEntry {
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neg_cost: 0,
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inbound_dir: None,
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inbound_dir_count: 0,
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inbound: None,
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pos: start,
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});
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while let Some(entry) = queue.pop() {
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for edge in self.edges_from(entry.pos, entry.inbound_dir) {
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if entry.inbound_dir.is_some_and(|d| d == edge.direction)
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&& entry.inbound_dir_count >= max_single_direction
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{
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continue;
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}
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let alt = distances[entry.pos.1 as usize][entry.pos.0 as usize]
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[entry.inbound_dir.unwrap_or(Direction::Right) as usize]
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[entry.inbound_dir_count]
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+ edge.cost as usize;
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let new_inbound_dir_count =
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if entry.inbound_dir.is_some_and(|d| d == edge.direction) {
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entry.inbound_dir_count + 1
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} else {
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1
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let entry_key = HistoryKey {
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pos: entry.pos,
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inbound: entry.inbound,
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};
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if alt
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< distances[edge.dest.1 as usize][edge.dest.0 as usize][edge.direction as usize]
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[new_inbound_dir_count]
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{
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distances[edge.dest.1 as usize][edge.dest.0 as usize]
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[edge.direction as usize][new_inbound_dir_count] = alt;
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prev[edge.dest.1 as usize][edge.dest.0 as usize][edge.direction as usize]
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[new_inbound_dir_count] = Some((
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entry.pos,
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entry.inbound_dir.map(|x| (x, entry.inbound_dir_count)),
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));
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queue.push(QueueEntry {
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neg_cost: -(alt as isize),
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inbound_dir: Some(edge.direction),
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inbound_dir_count: new_inbound_dir_count,
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for edge in edges_fn(self, entry.pos, entry.inbound) {
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let alt = distances.get(&entry_key).unwrap_or(&usize::MAX) + edge.cost as usize;
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let new_inbound_dir_count = if let Some((d, c)) = entry.inbound {
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if d == edge.direction {
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c + edge.steps
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} else {
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edge.steps
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}
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} else {
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edge.steps
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};
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let edge_key = HistoryKey {
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pos: edge.dest,
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});
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inbound: Some((edge.direction, new_inbound_dir_count)),
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};
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if alt < *distances.get(&edge_key).unwrap_or(&usize::MAX) {
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distances.insert(edge_key, alt);
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prev.insert(edge_key, entry_key);
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let new_entry = QueueEntry {
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neg_cost: -(alt as isize),
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inbound: Some((edge.direction, new_inbound_dir_count)),
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pos: edge.dest,
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};
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queue.push(new_entry);
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}
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}
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}
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for row in 0..self.height {
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for col in 0..self.width {
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println!("({}, {}) ", col, row);
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for d in Direction::all() {
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println!(
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"\t{:?} 0={}/{:?}, 1={}/{:?}, 2={}/{:?}, 3={}/{:?}",
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d,
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distances[row][col][d as usize][0],
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prev[row][col][d as usize][0],
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distances[row][col][d as usize][1],
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prev[row][col][d as usize][1],
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distances[row][col][d as usize][2],
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prev[row][col][d as usize][2],
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distances[row][col][d as usize][3],
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prev[row][col][d as usize][3],
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);
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}
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}
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}
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// for row in 0..self.height {
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// for col in 0..self.width {
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// println!("({}, {}) ", col, row);
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// for d in Direction::all() {
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// println!(
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// "\t{:?} 0={}/{:?}, 1={}/{:?}, 2={}/{:?}, 3={}/{:?}",
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// d,
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// distances[row][col][d as usize][0],
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// prev[row][col][d as usize][0],
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// distances[row][col][d as usize][1],
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// prev[row][col][d as usize][1],
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// distances[row][col][d as usize][2],
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// prev[row][col][d as usize][2],
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// distances[row][col][d as usize][3],
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// prev[row][col][d as usize][3],
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// );
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// }
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// }
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// }
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let mut path = vec![];
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let mut min = None;
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for (d, d_count) in Direction::all().into_iter().cartesian_product(0..4) {
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let cost = distances[end.1 as usize][end.0 as usize][d as usize][d_count];
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if min.is_none() || min.is_some_and(|(c, _, _)| c > cost) {
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min = Some((cost, d, d_count));
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}
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}
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let mut u = Some((end, min.map(|(_, d, dc)| (d, dc))));
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while let Some((p, dir_and_count)) = u {
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if let Some((dir, dir_count)) = dir_and_count {
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println!("dir={:?}, dir_count={}", dir, dir_count);
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}
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path.insert(0, p);
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u = dir_and_count.and_then(|(d, dc)| prev[p.1 as usize][p.0 as usize][d as usize][dc]);
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let min = distances
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.iter()
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.filter(|(k, _)| k.pos == end)
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.min_by_key(|(_, d)| **d)
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.unwrap()
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.0;
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let mut u = Some(min);
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while let Some(key) = u {
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println!("({}, {})", key.pos.0, key.pos.1);
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path.insert(0, key.pos);
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u = prev.get(key);
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}
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Some(path)
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}
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@ -274,6 +304,24 @@ impl Map {
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.map(|&(col, row)| self.costs[row as usize][col as usize] as usize)
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.sum()
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}
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fn part2_path_cost(&self, path: &[(isize, isize)]) -> usize {
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let mut cost = 0;
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for (a, b) in path.iter().zip(path.iter().skip(1)) {
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// a->b is always a cardinal direction, so one of these loops will only have one
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// iteration
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for row in a.1.min(b.1)..=a.1.max(b.1) {
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for col in a.0.min(b.0)..=a.0.max(b.0) {
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cost += self.costs[row as usize][col as usize] as usize;
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}
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}
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// don't double count the beginning of each path segment
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// also don't count the beginning of the first segment
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cost -= self.costs[a.1 as usize][a.0 as usize] as usize;
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}
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cost
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}
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}
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#[cfg(test)]
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@ -288,7 +336,7 @@ mod tests {
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"#
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.into();
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assert_eq!(
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map.dijkstra_ish((0, 0), (4, 1), 3),
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map.dijkstra_ish((0, 0), (4, 1), Map::part1_edges),
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Some(vec![(0, 0), (1, 0), (2, 0), (3, 0), (3, 1), (4, 1)])
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);
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}
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@ -301,7 +349,11 @@ mod tests {
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"#
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.into();
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assert_eq!(
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map.dijkstra_ish((0, 0), (map.width as isize - 1, map.height as isize - 1), 3),
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map.dijkstra_ish(
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(0, 0),
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(map.width as isize - 1, map.height as isize - 1),
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Map::part1_edges
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),
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Some(vec![(0, 0), (1, 0), (2, 0), (2, 1), (3, 1), (4, 1)])
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);
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}
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@ -324,8 +376,75 @@ mod tests {
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4322674655533
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"#
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.into();
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let path =
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dbg!(map.dijkstra_ish((0, 0), (map.width as isize - 1, map.height as isize - 1), 3));
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let path = dbg!(map.dijkstra_ish(
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(0, 0),
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(map.width as isize - 1, map.height as isize - 1),
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Map::part1_edges
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));
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assert_eq!(map.path_cost(&path.unwrap()), 102);
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}
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#[test]
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fn test_part2_example1() {
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let map: Map = r#"
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2413432311323
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3215453535623
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3255245654254
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3446585845452
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4546657867536
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1438598798454
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4457876987766
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3637877979653
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4654967986887
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4564679986453
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1224686865563
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2546548887735
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4322674655533
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"#
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.into();
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let path = dbg!(map.dijkstra_ish(
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(0, 0),
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(map.width as isize - 1, map.height as isize - 1),
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Map::part2_edges
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));
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assert_eq!(map.part2_path_cost(&path.unwrap()), 94);
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}
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#[test]
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fn test_part2_example2() {
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let map: Map = r#"
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111111111111
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999999999991
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999999999991
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999999999991
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999999999991
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"#
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.into();
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let path = dbg!(map.dijkstra_ish(
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(0, 0),
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(map.width as isize - 1, map.height as isize - 1),
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Map::part2_edges
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));
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assert_eq!(map.part2_path_cost(&path.unwrap()), 71);
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}
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#[test]
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fn test_part2_input_subgrid() {
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let map: Map = r#"
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645655655636632423532352254234
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353344463432453352632231125552
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526342234456245465642135234421
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346523323446362131122522334552
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344544334245121341153154552255
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545315342221553551233455324225
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312521155444131243522241333531
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153145243235542533153124432435
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133522524342325151543155414215
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"#
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.into();
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assert_eq!(
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map.part2_path_cost(&[(0, 8), (9, 8), (9, 4), (19, 4), (19, 0), (29, 0),]),
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110
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);
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}
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}
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