day20: part 2 solution (slow)

src/day20.rs

@@ -1,33 +1,36 @@
-use aoc_runner_derive::aoc;
-use grid::{AsCoord2d, Coord2d, Grid};
-use itertools::Itertools;
-use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
 use std::collections::VecDeque;
 
+use aoc_runner_derive::aoc;
+use grid::Grid;
+
 struct RaceTrack {
     map: Grid<u8>,
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
 struct State {
-    pos: Coord2d,
+    pos: (i64, i64),
     cost: u64,
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 struct CheatState {
     s: State,
+    p: Vec<(i64, i64)>,
 }
 
 const DIRECTIONS: [(i64, i64); 4] = [(-1, 0), (1, 0), (0, -1), (0, 1)];
 
 impl RaceTrack {
-    fn valid_moves<'a>(&'a self, CheatState { s: state }: &'a CheatState) -> impl Iterator<Item = CheatState> + 'a {
+    fn valid_moves<'a>(&'a self, CheatState { s: state, p }: &'a CheatState) -> impl Iterator<Item = CheatState> + 'a {
+        let mut new_path = p.clone();
+        new_path.push(state.pos);
         DIRECTIONS
             .iter()
-            .map(|dir| state.pos + dir)
+            .map(|dir| (state.pos.0 + dir.0, state.pos.1 + dir.1))
             .filter_map(move |pos| match &self.map.get(&pos) {
                 Some(b'.') | Some(b'S') | Some(b'E') => Some(CheatState {
+                    p: new_path.clone(),
                     s: State {
                         pos,
                         cost: state.cost + 1,
@@ -36,19 +39,22 @@ impl RaceTrack {
                 _ => None,
             })
     }
-    fn path_costs(&self, start: Coord2d, goal: Coord2d) -> Grid<Option<u64>> {
+    fn path_costs(&self, start: (i64, i64), goal: (i64, i64)) -> (Vec<(i64, i64)>, Grid<Option<u64>>) {
         let mut queue = VecDeque::new();
         let mut visited = self.map.same_shape(None);
 
         let start_state = CheatState {
             s: State { pos: start, cost: 0 },
+            p: Vec::new(),
         };
         visited.set(&start, Some(0));
         queue.push_back(start_state);
 
         while let Some(state) = queue.pop_front() {
             if state.s.pos == goal {
-                return visited;
+                let mut final_path = state.p;
+                final_path.push(goal);
+                return (final_path, visited);
             }
 
             let moves = self.valid_moves(&state);
@@ -63,49 +69,70 @@ impl RaceTrack {
         panic!("no path");
     }
 
-    fn find_cheats(&self, path: &Vec<Coord2d>, costs: &Grid<Option<u64>>, min: u64) -> i64 {
+    fn find_cheats(
-        let mut n = 0;
+        &self,
+        path: &Vec<(i64, i64)>,
+        costs: &Grid<Option<u64>>,
+        min: u64,
+    ) -> Vec<((i64, i64), (i64, i64), u64)> {
+        let mut cheats = Vec::new();
         for pos in path {
             let local_cost = costs.get(pos).unwrap().unwrap();
             for ofs in DIRECTIONS {
-                let cheat_exit = (pos.x() + ofs.0 * 2, pos.y() + ofs.1 * 2);
+                let cheat_start = (pos.0 + ofs.0, pos.1 + ofs.1);
+                let cheat_exit = (pos.0 + ofs.0 * 2, pos.1 + ofs.1 * 2);
                 if let Some(Some(cheat_cost)) = costs.get(&cheat_exit) {
                     if *cheat_cost > local_cost + 2 {
                         let cheat_savings = cheat_cost - local_cost - 2;
                         if cheat_savings >= min {
-                            n += 1;
+                            cheats.push((cheat_start, cheat_exit, cheat_savings));
                         }
                     }
                 }
             }
         }
-        n
+        cheats
     }
 
-    fn taxi_dist<A: AsCoord2d, B: AsCoord2d>(from: &A, to: &B) -> u64 {
+    fn taxi_dist(&self, from: &(i64, i64), to: &(i64, i64)) -> Option<u64> {
-        from.x().abs_diff(to.x()) + from.y().abs_diff(to.y())
+        if self.map.is_valid(to) {
+            Some(from.0.abs_diff(to.0) + from.1.abs_diff(to.1))
+        } else {
+            None
+        }
     }
 
-    fn find_cheats_n(&self, path: &Vec<Coord2d>, costs: &Grid<Option<u64>>, max_length: u64, min: u64) -> i64 {
+    fn find_cheats_n(
-        path.par_iter()
+        &self,
-            .map_with(costs, |costs, pos| {
+        path: &Vec<(i64, i64)>,
+        costs: &Grid<Option<u64>>,
+        max_length: u64,
+        min: u64,
+    ) -> Vec<((i64, i64), (i64, i64))> {
+        let mut cheats = Vec::new();
+        let mut solutions = self.map.clone();
+
+        for pos in path {
             let from_cost = costs.get(pos).unwrap().unwrap();
-                let mut n = 0;
+            for x in 0..self.map.width() as i64 {
-                for x in pos.x - max_length as i64 - 1..=pos.x + max_length as i64 {
+                for y in 0..self.map.height() as i64 {
-                    for y in pos.y - max_length as i64 - 1..=pos.y + max_length as i64 {
+                    if let Some(dist) = self.taxi_dist(pos, &(x, y)) {
-                        let dist = Self::taxi_dist(pos, &(x, y));
                         if dist <= max_length && dist >= 2 {
-                            if let Some(Some(to_cost)) = costs.get(&(x, y)) {
+                            if let Some(to_cost) = costs.get(&(x, y)).unwrap() {
+                                solutions.set(pos, b'O');
+                                solutions.set(&(x, y), b'O');
                                 if *to_cost > (from_cost + dist) && (to_cost - (from_cost + dist) >= min) {
-                                    n += 1;
+                                    cheats.push((*pos, (x, y)));
                                 }
                             }
                         }
                     }
+                    solutions.set(&(x, y), *self.map.get(&(x, y)).unwrap());
                 }
-                n
+            }
-            })
+            solutions.set(pos, *self.map.get(pos).unwrap());
-            .sum()
+        }
+        cheats
     }
 }
 
@@ -118,30 +145,20 @@ fn part1_impl(input: &str, cheat_min: u64) -> i64 {
     let track = parse(input);
     let start = track.map.find(&b'S').unwrap();
     let goal = track.map.find(&b'E').unwrap();
-    let costs = track.path_costs(start, goal);
+    let (best_path, costs) = track.path_costs(start.into(), goal.into());
-    let path_squares = costs
+    let cheats = track.find_cheats(&best_path, &costs, cheat_min);
-        .data
+
-        .iter()
+    cheats.len() as i64
-        .enumerate()
-        .filter(|(_i, c)| c.is_some())
-        .filter_map(|(i, _)| track.map.coord(i as i64))
-        .collect_vec();
-    track.find_cheats(&path_squares, &costs, cheat_min)
 }
 
 fn part2_impl(input: &str, max_length: u64, cheat_min: u64) -> i64 {
     let track = parse(input);
     let start = track.map.find(&b'S').unwrap();
     let goal = track.map.find(&b'E').unwrap();
-    let costs = track.path_costs(start, goal);
+    let (best_path, costs) = track.path_costs(start.into(), goal.into());
-    let path_squares = costs
+    let cheats = track.find_cheats_n(&best_path, &costs, max_length, cheat_min);
-        .data
+
-        .iter()
+    cheats.len() as i64
-        .enumerate()
-        .filter(|(_i, c)| c.is_some())
-        .filter_map(|(i, _)| track.map.coord(i as i64))
-        .collect_vec();
-    track.find_cheats_n(&path_squares, &costs, max_length, cheat_min)
 }
 
 #[aoc(day20, part1)]

src/day22.rs

@@ -1,4 +1,4 @@
-use aoc_runner_derive::aoc;
+use aoc_runner_derive::{aoc, aoc_generator};
 use itertools::Itertools;
 use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
 
@@ -31,7 +31,7 @@ fn prices(mut secret: i64, n: i64) -> Vec<i8> {
     prices
 }
 
-fn changes(prices: &[i8]) -> Vec<Change> {
+fn changes(prices: &Vec<i8>) -> Vec<Change> {
     prices
         .windows(2)
         .map(|a| Change {
@@ -45,10 +45,14 @@ fn profit_for_sequence(changes: &Vec<Vec<Change>>, seq: &[i8]) -> i64 {
     changes
         .par_iter()
         .filter_map(|inner| {
-            inner
+            if let Some(buy) = inner
                 .windows(seq.len())
                 .find(|window| window.iter().zip(seq).all(|(w, z)| w.delta == *z))
-                .map(|buy| buy[seq.len() - 1].price as i64)
+            {
+                Some(buy[seq.len() - 1].price as i64)
+            } else {
+                None
+            }
         })
         .sum()
 }
@@ -56,7 +60,7 @@ fn profit_for_sequence(changes: &Vec<Vec<Change>>, seq: &[i8]) -> i64 {
 fn find_best_sequence(changes: &Vec<Vec<Change>>) -> [i8; 4] {
     let mut best_seq = [0, 0, 0, 0];
     let mut best_profit = 0;
-    for seq in (0..4).map(|_| (-9..=9i8)).multi_cartesian_product() {
+    for seq in (0..4).map(|_| (-9..=9 as i8)).multi_cartesian_product() {
         let profit = profit_for_sequence(changes, &seq);
         if profit > best_profit {
             best_seq = seq.try_into().unwrap();
@@ -71,14 +75,14 @@ fn parse(input: &str) -> Vec<i64> {
 }
 
 #[aoc(day22, part1)]
-pub fn part1(input: &str) -> i64 {
+fn part1(input: &str) -> i64 {
     let secrets = parse(input);
 
     secrets.iter().map(|s| rounds(*s, 2000)).sum::<i64>()
 }
 
 #[aoc(day22, part2)]
-pub fn part2(input: &str) -> i64 {
+fn part2(input: &str) -> i64 {
     let secrets = parse(input);
 
     let price_changes = secrets.iter().map(|s| changes(&prices(*s, 2000))).collect_vec();
@@ -128,7 +132,10 @@ mod tests {
         let secrets = parse(EXAMPLE2);
 
         let price_changes = secrets.iter().map(|s| changes(&prices(*s, 2000))).collect_vec();
-        assert_eq!(profit_for_sequence(&price_changes, &[-2, 1, -1, 3]), 23);
+        assert_eq!(
+            profit_for_sequence(&price_changes, &[-2, 1, -1, 3]),
+            23
+        );
     }
 
     #[test]

src/lib.rs

@@ -12,7 +12,6 @@ pub mod day19;
 pub mod day2;
 pub mod day20;
 pub mod day21;
-pub mod day22;
 pub mod day3;
 pub mod day4;
 pub mod day5;

utils/grid/lib.rs

@@ -39,16 +39,6 @@ impl<T: AsCoord2d> Add<T> for &Coord2d {
     }
 }
 
-impl<T: AsCoord2d> Add<&T> for Coord2d {
-    type Output = Coord2d;
-    fn add(self, rhs: &T) -> Self::Output {
-        Coord2d {
-            x: self.x() + rhs.x(),
-            y: self.y() + rhs.y(),
-        }
-    }
-}
-
 impl AsCoord2d for Coord2d {
     fn to_coord(self) -> Coord2d {
         self
@@ -92,25 +82,6 @@ where
     }
 }
 
-impl<T> AsCoord2d for &(T, T)
-where
-    T: Copy + TryInto<i64>,
-    <T as TryInto<i64>>::Error: Debug,
-{
-    fn to_coord(self) -> Coord2d {
-        Coord2d {
-            x: self.0.try_into().unwrap(),
-            y: self.1.try_into().unwrap(),
-        }
-    }
-    fn x(&self) -> i64 {
-        self.0.try_into().unwrap()
-    }
-    fn y(&self) -> i64 {
-        self.1.try_into().unwrap()
-    }
-}
-
 impl From<Coord2d> for (i64, i64) {
     fn from(value: Coord2d) -> Self {
         (value.x, value.y)