Implement a circular queue data structure with a fixed size. You'll need to handle enqueueing, dequeueing, and checking if the queue is full or empty efficiently.

Find all unique triplets in an array that sum to zero. You'll need to consider the potential for duplicate numbers and avoid duplicate triplets in your solution.

Find all unique quadruplets in an array that sum to a target value. You'll need to efficiently search for combinations of four numbers that satisfy the given condition.