Queue Implementation

You can implement queues with:

$1.$ Linked list: $O(1)$ enqueue and dequeue, but more memory overhead.

$2.$ Circular array: $O(1)$ amortized, more cache-friendly. In practice, use the built-in: C++ has queue, Python has collections.deque (use append and popleft), Java has Queue interface with LinkedList. Don't implement from scratch in contests. Use the standard library. Time: $O(1)$ per operation. Space: $O(n)$.