Change A* heuristic to be a proper estimate

This makes it:
- Actually find the path with the fewest number of moves, and
- Not be so prone to getting stuck exploring space that seems "close to
  a solution" but is actually a dead end.

Cargo.lock

@@ -23,19 +23,46 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "64fa3c856b712db6612c019f14756e64e4bcea13337a6b33b696333a9eaa2d06"
 
+[[package]]
+name = "cfg-if"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2fd1289c04a9ea8cb22300a459a72a385d7c73d3259e2ed7dcb2af674838cfa9"
+
 [[package]]
 name = "fast-srgb8"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dd2e7510819d6fbf51a5545c8f922716ecfb14df168a3242f7d33e0239efe6a1"
 
+[[package]]
+name = "getrandom"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26145e563e54f2cadc477553f1ec5ee650b00862f0a58bcd12cbdc5f0ea2d2f4"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi",
+ "wasi",
+]
+
 [[package]]
 name = "hanoigame"
 version = "0.1.0"
 dependencies = [
  "palette",
+ "rand 0.9.2",
+ "rand_pcg",
+ "rand_seeder",
 ]
 
+[[package]]
+name = "libc"
+version = "0.2.175"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a82ae493e598baaea5209805c49bbf2ea7de956d50d7da0da1164f9c6d28543"
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -86,7 +113,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3c80231409c20246a13fddb31776fb942c38553c51e871f8cbd687a4cfb5843d"
 dependencies = [
  "phf_shared",
- "rand",
+ "rand 0.8.5",
 ]
 
 [[package]]
@@ -111,6 +138,15 @@ dependencies = [
  "siphasher",
 ]
 
+[[package]]
+name = "ppv-lite86"
+version = "0.2.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85eae3c4ed2f50dcfe72643da4befc30deadb458a9b590d720cde2f2b1e97da9"
+dependencies = [
+ "zerocopy",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.101"
@@ -129,13 +165,39 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r-efi"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
+
 [[package]]
 name = "rand"
 version = "0.8.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
 dependencies = [
- "rand_core",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db2770f06117d490610c7488547d543617b21bfa07796d7a12f6f1bd53850d1"
+dependencies = [
+ "rand_chacha",
+ "rand_core 0.9.3",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.9.3",
 ]
 
 [[package]]
@@ -144,6 +206,33 @@ version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
 
+[[package]]
+name = "rand_core"
+version = "0.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "99d9a13982dcf210057a8a78572b2217b667c3beacbf3a0d8b454f6f82837d38"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "rand_pcg"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b48ac3f7ffaab7fac4d2376632268aa5f89abdb55f7ebf8f4d11fffccb2320f7"
+dependencies = [
+ "rand_core 0.9.3",
+]
+
+[[package]]
+name = "rand_seeder"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "502927fdfc3c9645d53e0c95bb2d53783b5a15bfeaeeb96f7703c21fbb76841e"
+dependencies = [
+ "rand_core 0.9.3",
+]
+
 [[package]]
 name = "siphasher"
 version = "1.0.1"
@@ -166,3 +255,38 @@ name = "unicode-ident"
 version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5a5f39404a5da50712a4c1eecf25e90dd62b613502b7e925fd4e4d19b5c96512"
+
+[[package]]
+name = "wasi"
+version = "0.14.3+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a51ae83037bdd272a9e28ce236db8c07016dd0d50c27038b3f407533c030c95"
+dependencies = [
+ "wit-bindgen",
+]
+
+[[package]]
+name = "wit-bindgen"
+version = "0.45.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "052283831dbae3d879dc7f51f3d92703a316ca49f91540417d38591826127814"
+
+[[package]]
+name = "zerocopy"
+version = "0.8.26"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1039dd0d3c310cf05de012d8a39ff557cb0d23087fd44cad61df08fc31907a2f"
+dependencies = [
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.8.26"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ecf5b4cc5364572d7f4c329661bcc82724222973f2cab6f050a4e5c22f75181"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]

Cargo.toml

@@ -5,5 +5,8 @@ edition = "2024"
 
 [dependencies]
 palette = "0.7"
+rand = "0.9.2"
+rand_pcg = "0.9.0"
+rand_seeder = "0.4.0"
 
 [workspace]

src/main.rs

@@ -1,4 +1,7 @@
 use palette::{IntoColor, OklabHue, Oklch, Srgb};
+use rand::seq::SliceRandom as _;
+use rand_pcg::Pcg64;
+use rand_seeder::Seeder;
 use std::{
     collections::{BinaryHeap, HashMap, HashSet},
     fmt::Display,
@@ -319,22 +322,8 @@ impl<const TOWER_HEIGHT: usize> Game<TOWER_HEIGHT> {
             hasher.finish()
         };
 
-        #[derive(PartialEq)]
-        struct Ordf32(f32);
-        impl Eq for Ordf32 {}
-        impl PartialOrd for Ordf32 {
-            fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-                Some(self.cmp(other))
-            }
-        }
-        impl Ord for Ordf32 {
-            fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-                self.0.total_cmp(&other.0)
-            }
-        }
-
         let mut states = Vec::new();
-        let mut todo = BinaryHeap::<(Ordf32, usize, usize)>::new();
+        let mut todo = BinaryHeap::<((i64, i64), i64, usize)>::new();
         let mut had = HashSet::new();
         let mut ctr = 0;
 
@@ -343,7 +332,7 @@ impl<const TOWER_HEIGHT: usize> Game<TOWER_HEIGHT> {
             parent_index: 0,
             m: Move::new(0, 0),
         });
-        todo.push((Ordf32(0.0), 1000000000, 0));
+        todo.push(((0, 0), 1000000000, 0));
 
         while let Some((score, depth, state_index)) = todo.pop() {
             ctr += 1;
@@ -384,8 +373,36 @@ impl<const TOWER_HEIGHT: usize> Game<TOWER_HEIGHT> {
                 working_instance.towers = state.towers.clone();
                 working_instance.make_move(m).unwrap();
 
-                let num_solved = working_instance.num_solved();
+                let brs: i64 = {
-                let brs = working_instance.burried_ring_score();
+                    let this = &working_instance;
+                    let mut seen_bottom_rings = HashSet::new();
+                    this.towers
+                        .iter()
+                        .map(|i| {
+                            let this = &i;
+                            let mut ring_type = None;
+                            let mut burried_score = 0;
+
+                            for ring in this.rings.iter().rev().flatten() {
+                                if let Some(existing_ring_type) = ring_type
+                                    && existing_ring_type != *ring
+                                {
+                                    burried_score += 1;
+                                }
+                                ring_type = Some(*ring);
+                            }
+                            if let Some(Some(ring)) = this.rings.last() {
+                                if seen_bottom_rings.contains(ring) {
+                                    burried_score += 1;
+                                } else {
+                                    seen_bottom_rings.insert(ring);
+                                }
+                            }
+
+                            burried_score
+                        })
+                        .sum()
+                };
 
                 let new_state_hash = hash_state(&working_instance.towers);
                 if had.contains(&new_state_hash) {
@@ -399,9 +416,11 @@ impl<const TOWER_HEIGHT: usize> Game<TOWER_HEIGHT> {
                     m,
                 });
 
-                let score = (num_solved as f32 * 10.0) + (-(brs as f32) * 100.0);
+                let score = (depth) - (brs);
-
+                // if ctr % 10000 == 0 {
-                todo.push((Ordf32(score), depth - 1, new_state_index));
+                //     dbg!(brs, depth, score);
+                // }
+                todo.push(((score, -depth), depth - 1, new_state_index));
             }
         }
 
@@ -643,15 +662,16 @@ pub struct GameGenerator {
 }
 
 impl GameGenerator {
-    pub fn generate<const TOWER_HEIGHT: usize>(self) -> Game<TOWER_HEIGHT> {
+    pub fn generate<const TOWER_HEIGHT: usize>(self, rng: &mut Pcg64) -> Game<TOWER_HEIGHT> {
         let mut towers = Vec::new();
-        let mut rings = HashSet::new();
+        let mut rings = Vec::new();
 
         for ring_type in 0..self.num_ring_types {
             for idx in 0..TOWER_HEIGHT {
-                rings.insert((Ring(NonZero::new(ring_type + 1).unwrap()), idx));
+                rings.push((Ring(NonZero::new(ring_type + 1).unwrap()), idx));
             }
         }
+        rings.shuffle(rng);
 
         let rings = rings.into_iter().map(|(i, _)| i).collect::<Vec<_>>();
 
@@ -666,9 +686,13 @@ impl GameGenerator {
         Game::new(towers)
     }
 
-    pub fn highest_burried_score<const TOWER_HEIGHT: usize>(self) -> Game<TOWER_HEIGHT> {
+    pub fn highest_burried_score<const TOWER_HEIGHT: usize>(
+        self,
+        seed: &str,
+    ) -> Game<TOWER_HEIGHT> {
+        let mut rng: Pcg64 = Seeder::from(seed).into_rng();
         iter::repeat(self)
-            .map(|i| i.generate())
+            .map(|i| i.generate(&mut rng))
             .take(100)
             .max_by_key(|i| i.burried_ring_score())
             .unwrap()
@@ -748,11 +772,15 @@ impl<const TOWER_HEIGHT: usize> Default for UndoStack<TOWER_HEIGHT> {
 }
 
 fn main() -> io::Result<()> {
+    eprint!("seed> ");
+    let mut seed = String::new();
+    stdin().read_line(&mut seed).unwrap();
+
     let mut g = GameGenerator {
         num_extra_towers: 2,
         num_ring_types: 13,
     }
-    .highest_burried_score::<4>();
+    .highest_burried_score::<4>(&seed);
 
     if let Some(solution) = g.solve() {
         let mut g = Game {