Method __lt__

8_puzzle.py:20–22

For PriorityQueue ordering: compare priorities.

(self, other: "PuzzleState")

        self.previous = previous  # Previous state in solution path

    def __lt__(self, other: "PuzzleState") -> bool:
        """For PriorityQueue ordering: compare priorities."""
        return self.priority() < other.priority()

    def priority(self) -> int:
        """A* priority: moves + Manhattan distance."""