day22: improvements

README.md

@@ -1,6 +1,6 @@
 <!-- AOC TILES BEGIN -->
 <h1 align="center">
-  2024 - 40 ⭐ - Rust
+  2024 - 43 ⭐ - Rust
 </h1>
 <a href="src/day1.rs">
   <img src=".aoc_tiles/tiles/2024/01.png" width="161px">
@@ -65,4 +65,7 @@
 <a href="src/day21.rs">
   <img src=".aoc_tiles/tiles/2024/21.png" width="161px">
 </a>
+<a href="src/day22.rs">
+  <img src=".aoc_tiles/tiles/2024/22.png" width="161px">
+</a>
 <!-- AOC TILES END -->

src/day20.rs

@@ -1,18 +1,8 @@
-use std::{
-    cmp::Reverse,
-    collections::{BinaryHeap, VecDeque},
-};
-
 use aoc_runner_derive::aoc;
-use grid::Grid;
-use rustc_hash::{FxHashMap, FxHashSet};
-
-trait PathTrack {
-    const DOES_WORK: bool = true;
-    fn new() -> Self;
-    fn push(&mut self, pos: (i64, i64));
-    fn finalize(&mut self) {}
-}
+use grid::{AsCoord2d, Coord2d, Grid};
+use itertools::Itertools;
+use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+use std::collections::VecDeque;
 
 struct RaceTrack {
     map: Grid<u8>,
@@ -20,28 +10,24 @@ struct RaceTrack {
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
 struct State {
-    pos: (i64, i64),
-    cost: usize,
+    pos: Coord2d,
+    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, p }: &'a CheatState) -> impl Iterator<Item = CheatState> + 'a {
-        let mut new_path = p.clone();
-        new_path.push(state.pos);
+    fn valid_moves<'a>(&'a self, CheatState { s: state }: &'a CheatState) -> impl Iterator<Item = CheatState> + 'a {
         DIRECTIONS
             .iter()
-            .map(|dir| (state.pos.0 + dir.0, state.pos.1 + dir.1))
+            .map(|dir| state.pos + dir)
             .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,
@@ -50,25 +36,19 @@ impl RaceTrack {
                 _ => None,
             })
     }
-    fn path_costs(&self, start: (i64, i64), goal: (i64, i64)) -> (Vec<(i64, i64)>, Grid<Option<usize>>) {
+    fn path_costs(&self, start: Coord2d, goal: Coord2d) -> 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: 0usize,
-            },
-            p: Vec::new(),
+            s: State { pos: start, cost: 0 },
         };
         visited.set(&start, Some(0));
         queue.push_back(start_state);
 
         while let Some(state) = queue.pop_front() {
             if state.s.pos == goal {
-                let mut final_path = state.p;
-                final_path.push(goal);
-                return (final_path, visited);
+                return visited;
             }
 
             let moves = self.valid_moves(&state);
@@ -83,29 +63,49 @@ impl RaceTrack {
         panic!("no path");
     }
 
-    fn find_cheats(
-        &self,
-        path: &Vec<(i64, i64)>,
-        costs: &Grid<Option<usize>>,
-        min: usize,
-    ) -> Vec<((i64, i64), (i64, i64), usize)> {
-        let mut cheats = Vec::new();
+    fn find_cheats(&self, path: &Vec<Coord2d>, costs: &Grid<Option<u64>>, min: u64) -> i64 {
+        let mut n = 0;
         for pos in path {
             let local_cost = costs.get(pos).unwrap().unwrap();
             for ofs in DIRECTIONS {
-                let cheat_start = (pos.0 + ofs.0, pos.1 + ofs.1);
-                let cheat_exit = (pos.0 + ofs.0 * 2, pos.1 + ofs.1 * 2);
+                let cheat_exit = (pos.x() + ofs.0 * 2, pos.y() + 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 {
-                            cheats.push((cheat_start, cheat_exit, cheat_savings));
+                            n += 1;
                         }
                     }
                 }
             }
         }
-        cheats
+        n
+    }
+
+    fn taxi_dist<A: AsCoord2d, B: AsCoord2d>(from: &A, to: &B) -> u64 {
+        from.x().abs_diff(to.x()) + from.y().abs_diff(to.y())
+    }
+
+    fn find_cheats_n(&self, path: &Vec<Coord2d>, costs: &Grid<Option<u64>>, max_length: u64, min: u64) -> i64 {
+        path.par_iter()
+            .map_with(costs, |costs, pos| {
+                let from_cost = costs.get(pos).unwrap().unwrap();
+                let mut n = 0;
+                for x in pos.x - max_length as i64 - 1..=pos.x + max_length as i64 {
+                    for y in pos.y - max_length as i64 - 1..=pos.y + max_length as i64 {
+                        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 *to_cost > (from_cost + dist) && (to_cost - (from_cost + dist) >= min) {
+                                    n += 1;
+                                }
+                            }
+                        }
+                    }
+                }
+                n
+            })
+            .sum()
     }
 }
 
@@ -114,14 +114,34 @@ fn parse(input: &str) -> RaceTrack {
     RaceTrack { map }
 }
 
-fn part1_impl(input: &str, cheat_min: usize) -> i64 {
+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 (best_path, costs) = track.path_costs(start.into(), goal.into());
-    let cheats = track.find_cheats(&best_path, &costs, cheat_min);
+    let costs = track.path_costs(start, goal);
+    let path_squares = costs
+        .data
+        .iter()
+        .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)
+}
 
-    cheats.len() as i64
+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 path_squares = costs
+        .data
+        .iter()
+        .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)]
@@ -131,7 +151,7 @@ pub fn part1(input: &str) -> i64 {
 
 #[aoc(day20, part2)]
 pub fn part2(input: &str) -> i64 {
-    todo!()
+    part2_impl(input, 20, 100)
 }
 
 #[cfg(test)]
@@ -160,6 +180,7 @@ mod tests {
 
     #[test]
     fn part2_example() {
-        assert_eq!(part2(EXAMPLE), 0);
+        assert_eq!(part2_impl(EXAMPLE, 2, 0), 44);
+        assert_eq!(part2_impl(EXAMPLE, 20, 50), 285);
     }
 }

src/day22.rs

@@ -0,0 +1,156 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+
+#[derive(Debug, Eq, PartialEq, PartialOrd, Ord)]
+struct Change {
+    price: i8,
+    delta: i8,
+}
+
+fn evolve_secret(mut n: i64) -> i64 {
+    n = ((n * 64) ^ n) % 16777216;
+    n = ((n / 32) ^ n) % 16777216;
+    n = ((n * 2048) ^ n) % 16777216;
+    n
+}
+
+fn rounds(mut secret: i64, n: i64) -> i64 {
+    for _ in 0..n {
+        secret = evolve_secret(secret)
+    }
+    secret
+}
+
+fn prices(mut secret: i64, n: i64) -> Vec<i8> {
+    let mut prices = vec![(secret % 10) as i8];
+    for _ in 1..n {
+        secret = evolve_secret(secret);
+        prices.push((secret % 10) as i8);
+    }
+    prices
+}
+
+fn changes(prices: &[i8]) -> Vec<Change> {
+    prices
+        .windows(2)
+        .map(|a| Change {
+            price: a[1],
+            delta: a[1] - a[0],
+        })
+        .collect()
+}
+
+fn profit_for_sequence(changes: &Vec<Vec<Change>>, seq: &[i8]) -> i64 {
+    changes
+        .par_iter()
+        .filter_map(|inner| {
+            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)
+        })
+        .sum()
+}
+
+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() {
+        let profit = profit_for_sequence(changes, &seq);
+        if profit > best_profit {
+            best_seq = seq.try_into().unwrap();
+            best_profit = profit;
+        }
+    }
+    best_seq
+}
+
+fn parse(input: &str) -> Vec<i64> {
+    input.lines().map(|l| l.parse().unwrap()).collect()
+}
+
+#[aoc(day22, part1)]
+pub 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 {
+    let secrets = parse(input);
+
+    let price_changes = secrets.iter().map(|s| changes(&prices(*s, 2000))).collect_vec();
+
+    let seq = find_best_sequence(&price_changes);
+    println!("found best seq: {:?}", seq);
+    profit_for_sequence(&price_changes, &seq)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "1
+10
+100
+2024";
+
+    const EXAMPLE2: &str = "1
+2
+3
+2024";
+
+    #[test]
+    fn evolution() {
+        assert_eq!(evolve_secret(123), 15887950);
+        assert_eq!(evolve_secret(15887950), 16495136);
+        assert_eq!(evolve_secret(16495136), 527345);
+    }
+
+    #[test]
+    fn test_rounds() {
+        assert_eq!(rounds(1, 2000), 8685429);
+        assert_eq!(rounds(10, 2000), 4700978);
+    }
+
+    #[test]
+    fn test_prices() {
+        assert_eq!(prices(123, 10), vec![3, 0, 6, 5, 4, 4, 6, 4, 4, 2]);
+    }
+
+    #[test]
+    fn test_profit() {
+        assert_eq!(
+            profit_for_sequence(&vec![changes(&prices(123, 10))], &[-1, -1, 0, 2]),
+            6
+        );
+        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);
+    }
+
+    #[test]
+    fn test_changes() {
+        let changes = changes(&prices(123, 10));
+        assert_eq!(
+            changes.iter().map(|c| c.delta).collect_vec(),
+            vec![-3, 6, -1, -1, 0, 2, -2, 0, -2]
+        );
+        assert_eq!(
+            changes.iter().map(|c| c.price).collect_vec(),
+            vec![0, 6, 5, 4, 4, 6, 4, 4, 2]
+        );
+    }
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 37327623);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE2), 23);
+    }
+}

src/lib.rs

@@ -12,6 +12,7 @@ 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

@@ -39,6 +39,16 @@ 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
@@ -82,6 +92,25 @@ 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)