better iter order

card_game/src/lib.rs

@@ -405,6 +405,7 @@ where
 	pub fn is_winnable(&self) -> Option<Vec<StateSnapshot<G>>> {
 		let mut state_moves = std::collections::HashMap::new();
 		let mut state = self.clone();
+		let mut i: u64 = 0;
 		while !state.is_win() {
 			// Continue existing iterator if it exists
 			let it = state_moves
@@ -424,6 +425,33 @@ where
 				state.undo();
 			}
 		}
+
+		// 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);
+			}
+		}
+
 		Some(state.state.history)
 	}
 }

klondike/src/lib.rs

@@ -629,18 +629,19 @@ impl Klondike {
 			KlondikeInstruction::RotateStock => 4,
 		}
 	}
+	pub fn iter(&self) -> impl Iterator<Item = KlondikeInstruction> + use<> {
+		let state = self.state.clone();
+		KlondikeIter::new().filter(move |&instruction| state.is_instruction_valid(instruction))
+	}
 	/// A single move that usually makes progress towards a winning game
 	pub fn get_auto_move(&self) -> Option<KlondikeInstruction> {
-		self.possible_instructions()
+		self.iter()
 			.filter(|ins| !ins.is_useless())
 			.min_by_key(|ins| self.instruction_priority(ins))
 	}
 	/// A list of possible moves with useless moves filtered out and sorted by a simple priority function
 	pub fn get_sorted_moves(&self) -> Vec<KlondikeInstruction> {
-		let mut useful_moves: Vec<_> = self
+		let mut useful_moves: Vec<_> = self.iter().filter(|ins| !ins.is_useless()).collect();
-			.possible_instructions()
-			.filter(|ins| !ins.is_useless())
-			.collect();
 		useful_moves.sort_by_key(|ins| self.instruction_priority(ins));
 		useful_moves
 	}
@@ -651,8 +652,7 @@ impl Game for Klondike {
 	type Config = KlondikeConfig;
 	type Instruction = KlondikeInstruction;
 	fn possible_instructions(&self) -> impl Iterator<Item = Self::Instruction> + use<> {
-		let state = self.state.clone();
+		self.get_sorted_moves().into_iter()
-		KlondikeIter::new().filter(move |&instruction| state.is_instruction_valid(instruction))
 	}
 	fn is_instruction_valid(&self, _config: &Self::Config, instruction: Self::Instruction) -> bool {
 		self.state.is_instruction_valid(instruction)