Improvement: Year 2016: Day 13: Now using a common BFS algorithm ever…

…ywhere

CHANGELOG.md

@@ -10,6 +10,10 @@ Of note:
 - The changelog 2015.5.2 has been rewritten from each commit content.
 - This file may be amended entirely in the future to adhere to the [GNU Changelog style](https://www.gnu.org/prep/standards/html_node/Style-of-Change-Logs.html#Style-of-Change-Logs)
 
+## [2016.17.2]
+### Changed
+- Exercise for 2016, day 13, now uses the [BreadthFirstSearch](src/bfs.rs) lib.
+
 ## [2016.17.1]
 ### Added
 - Solved [exercice for 2016, day 17](src/year_2016/17.rs).

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "advent-rs"
-version = "2016.17.1"
+version = "2016.17.2"
 edition = "2021"
 authors = ["Arnaud 'red' Rouyer"]
 readme = "README.md"

NOTES_2016.md

@@ -80,3 +80,5 @@ Another thing of note is that if you know how to optimize your loop-down, you ca
 ## Day 17: Two Steps Forward
 
 A big part of this day was bout building a [BreadthFirstSearch library](src/bfs.rs) that would be flexible enough to reuse in other exercises, since there are SO MANY in this year.
+
+There was some confusion between all the generics, abstractions, and types, especially since this day got some strange rules (storing together position+path) but in the end, I think I got it, and implementing it on day 13 (which only got a position) was really fast, and execution time got faster too.

src/bfs.rs

@@ -10,7 +10,7 @@ where
   starting: POS,
   pub ending: Option<POS>,
   queue: VecDeque<(POS, usize)>,
-  visited: HashSet<POS>,
+  pub visited: HashSet<POS>,
   pub depth: usize,
   next_moves: NM,
 }
@@ -59,7 +59,7 @@ where
   }
 
   pub fn traverse_until_depth(&mut self, target_depth: usize) -> &mut Self {
-    self.traverse(|_position, depth| depth == target_depth, true)
+    self.traverse(|_position, depth| depth > target_depth, true)
   }
 
   pub fn traverse_until_position(&mut self, target_position: POS) -> &mut Self {

src/year_2016/day_13.rs

@@ -1,26 +1,4 @@
-use std::collections::HashSet;
-use std::collections::VecDeque;
-
-enum PositionOrCount {
-  Position((usize, usize)),
-  Count(u8),
-}
-
-impl PositionOrCount {
-  fn reached_position(&self, reach: (usize, usize)) -> bool {
-    match self {
-      PositionOrCount::Position(target) => *target == reach,
-      PositionOrCount::Count(_) => false,
-    }
-  }
-
-  fn reached_count(&self, steps_count: u8) -> bool {
-    match self {
-      PositionOrCount::Position(_) => false,
-      PositionOrCount::Count(count) => steps_count > *count,
-    }
-  }
-}
+use crate::bfs::BreadthFirstSearch;
 
 fn cell_is_wall(favorite: usize, position: (usize, usize)) -> bool {
   let x = position.0;
@@ -29,42 +7,22 @@ fn cell_is_wall(favorite: usize, position: (usize, usize)) -> bool {
   return value.count_ones() % 2 == 1;
 }
 
-fn next_moves(position: (usize, usize)) -> Vec<(usize, usize)> {
+fn next_moves(favorite: usize, position: (usize, usize)) -> Vec<(usize, usize)> {
   let mut new_moves: Vec<(usize, usize)> = vec![];
-  if position.0 > 0 {
+  if position.0 > 0 && !cell_is_wall(favorite, (position.0 - 1, position.1)) {
     new_moves.push((position.0 - 1, position.1));
   }
-  new_moves.push((position.0 + 1, position.1));
-  if position.1 > 0 {
+  if !cell_is_wall(favorite, (position.0 + 1, position.1)) {
+    new_moves.push((position.0 + 1, position.1));
+  }
+  if position.1 > 0 && !cell_is_wall(favorite, (position.0, position.1 - 1)) {
     new_moves.push((position.0, position.1 - 1));
   }
-  new_moves.push((position.0, position.1 + 1));
-
-  new_moves
-}
-
-fn traverse_until(favorite: usize, reach_condition: PositionOrCount) -> u8 {
-  let mut visited: HashSet<(usize, usize)> = HashSet::from([(1, 1)]);
-  let mut queue: VecDeque<((usize, usize), u8)> = VecDeque::from([((1, 1), 0)]);
-
-  while let Some((position, depth)) = queue.pop_front() {
-    if reach_condition.reached_position(position) {
-      return depth;
-    }
-    if reach_condition.reached_count(depth) {
-      return visited.len() as u8;
-    }
-
-    visited.insert(position);
-    for next_move in next_moves(position) {
-      if visited.contains(&next_move) || cell_is_wall(favorite, next_move) {
-        continue;
-      }
-      queue.push_back((next_move, depth + 1));
-    }
+  if !cell_is_wall(favorite, (position.0, position.1 + 1)) {
+    new_moves.push((position.0, position.1 + 1));
   }
 
-  0
+  new_moves
 }
 
 pub fn day_13_v1(input: impl Into<String>) -> u8 {
@@ -73,16 +31,20 @@ pub fn day_13_v1(input: impl Into<String>) -> u8 {
   let favorite = input_parts[0].parse::<usize>().unwrap();
   let reach_x = input_parts[1].parse::<usize>().unwrap();
   let reach_y = input_parts[2].parse::<usize>().unwrap();
+  let mut bfs = BreadthFirstSearch::new((1, 1), |position| next_moves(favorite, position));
+  bfs.traverse_until_position((reach_x, reach_y));
 
-  traverse_until(favorite, PositionOrCount::Position((reach_x, reach_y)))
+  bfs.depth as u8
 }
 
 pub fn day_13_v2(input: impl Into<String>) -> u8 {
   let binding = input.into();
   let input_parts: Vec<_> = binding.split(",").collect();
   let favorite = input_parts[0].parse::<usize>().unwrap();
+  let mut bfs = BreadthFirstSearch::new((1, 1), |position| next_moves(favorite, position));
+  bfs.traverse_until_depth(50);
 
-  traverse_until(favorite, PositionOrCount::Count(50))
+  bfs.visited.len() as u8
 }
 
 solvable!(day_13, day_13_v1, day_13_v2, u8);

src/year_2016/day_17.rs

@@ -16,7 +16,7 @@ impl Day17Position {
     }
   }
 
-  pub fn next_moves_for_hasher(&self, mut hasher: CoreWrapper<Md5Core>) -> Vec<Self> {
+  pub fn next_moves(&self, mut hasher: CoreWrapper<Md5Core>) -> Vec<Self> {
     hasher.update(self.path.clone());
     let positions: &[u8] = &hasher.finalize()[0..=1];
     let mut next_moves = vec![];
@@ -101,9 +101,7 @@ pub fn day_17_v1(input: impl Into<String>) -> String {
   let mut hasher = Md5::new();
   hasher.update(input.into().trim_end());
   let starter = Day17Position::new((0, 0));
-  let mut bfs = BreadthFirstSearch::new(starter, |curpos| {
-    curpos.next_moves_for_hasher(hasher.clone())
-  });
+  let mut bfs = BreadthFirstSearch::new(starter, |curpos| curpos.next_moves(hasher.clone()));
   bfs.traverse_until(|position| position.position == (3, 3));
 
   bfs.ending.unwrap().path
@@ -113,9 +111,7 @@ pub fn day_17_v2(input: impl Into<String>) -> String {
   let mut hasher = Md5::new();
   hasher.update(input.into().trim_end());
   let starter = Day17Position::new((0, 0));
-  let mut bfs = BreadthFirstSearch::new(starter, |curpos| {
-    curpos.next_moves_for_hasher(hasher.clone())
-  });
+  let mut bfs = BreadthFirstSearch::new(starter, |curpos| curpos.next_moves(hasher.clone()));
   bfs.longest_path_until(|position| position.position == (3, 3));
 
   bfs.depth.to_string()
@@ -135,12 +131,12 @@ mod tests {
       ("ulqzkmiv", "DRURDRUDDLLDLUURRDULRLDUUDDDRR"),
     ];
     for (sample, result) in sample_one {
-      println!("TEST => {}", sample);
       assert_eq!(day_17_v1(sample), result);
     }
   }
 
   #[test]
+  #[ignore = "Too slow for CI"]
   fn works_with_samples_v2() {
     let sample_two: [(&str, &str); 3] = [
       ("ihgpwlah", "370"),