ooh at 99% cap

card_game/src/lib.rs

@@ -321,6 +321,9 @@ impl<S> SessionStats<S> {
 	}
 }
 
+#[derive(Debug)]
+pub struct Oom;
+
 #[derive(Clone, Debug)]
 pub struct Session<G: Game> {
 	stats: SessionStats<G::Stats>,
@@ -402,10 +405,16 @@ where
 	pub fn is_win(&self) -> bool {
 		self.state.is_win()
 	}
-	pub fn is_winnable(&self) -> Option<Vec<StateSnapshot<G>>> {
+	pub fn is_winnable(&self) -> Result<Option<Vec<StateSnapshot<G>>>, Oom> {
-		let mut state_moves = std::collections::HashMap::new();
+		const HUGE_CAP: usize = 1 << 25;
+		let mut state_moves = std::collections::HashMap::with_capacity(HUGE_CAP);
 		let mut state = self.clone();
 		while !state.is_win() {
+			// don't look for empty hash map buckets when the hash map is 99% full!
+			if HUGE_CAP * 127 <= state_moves.len() * 128 {
+				return Err(Oom);
+			}
+
 			// Continue existing iterator if it exists
 			let it = state_moves
 				.entry(state.state().clone())
@@ -419,12 +428,39 @@ where
 
 			// No more moves. If we can't undo we're done
 			if state.history().is_empty() {
-				return None;
+				return Ok(None);
 			} else {
 				state.undo();
 			}
 		}
-		Some(state.state.history)
+
+		// history includes cycles
+		let mut state_index: std::collections::HashMap<_, _> = state
+			.history()
+			.iter()
+			.enumerate()
+			.map(|(i, snapshot)| (snapshot.state().clone(), i))
+			.collect();
+
+		// find the longest range where the start and end are the same state
+		while let Some(longest_range) = state
+			.history()
+			.iter()
+			.enumerate()
+			.filter_map(|(index, snapshot)| {
+				let &last_index = state_index.get(snapshot.state())?;
+				let longness = last_index - index;
+				(longness != 0).then_some(index..last_index)
+			})
+			.max_by_key(|range| range.len())
+		{
+			state.state.history.drain(longest_range);
+			for (i, snapshot) in state.history().iter().enumerate() {
+				state_index.insert(snapshot.state().clone(), i);
+			}
+		}
+
+		Ok(Some(state.state.history))
 	}
 }
 impl<G: Game> Game for SessionState<G>

klondike-cli/src/test.rs

@@ -3,31 +3,13 @@ use klondike::Klondike;
 #[test]
 fn test_is_winnable() {
 	// is winnable
-	let is_winnable = Session::new_default(Klondike::with_seed(123)).is_winnable();
+	let is_winnable = Session::new_default(Klondike::with_seed(0)).is_winnable().unwrap();
-	println!("is_winnable = {is_winnable:?}");
+	if let Some(win_moves) = is_winnable {
-}
+		// for (i, ins) in win_moves.into_iter().enumerate() {
-#[test]
+		// 	println!("{i} = {:?}", ins.instruction());
-fn test_klondike() {
+		// }
-	// create game session
+		println!("Game is winnable with {} moves", win_moves.len());
-	let game = Klondike::with_seed(123);
+	} else {
-	let mut session = Session::new_default(game);
+		println!("Game is not winnable");
-
-	// is winnable
-	let is_winnable = session.is_winnable();
-	println!("is_winnable = {is_winnable:?}");
-
-	// play game
-	while let Some(instruction) = session.possible_instructions().next() {
-		session.process_instruction(instruction);
 	}
-
-	// did win
-	let is_win = session.is_win();
-
-	// print session history
-	for (i, instruction) in session.history().iter().enumerate() {
-		println!("move {i} = {instruction:?}");
-	}
-
-	println!("is_win = {is_win}");
 }

klondike/src/lib.rs

@@ -533,6 +533,10 @@ impl Iterator for KlondikeIter {
 		instruction
 	}
 }
+#[test]
+fn test_klondike_iter() {
+	assert_eq!(KlondikeIter::new().count(), 721);
+}
 
 #[derive(Clone, Debug, Eq, Hash, PartialEq)]
 pub struct Klondike {