Implement a Circular Buffer/Ring Buffer

To implement a circular buffer efficiently, I would start by defining a structure containing a fixed-size array, two integer pointers for the head and tail, and a counter for the current number of elements. Using a counter is crucial because comparing head and tail alone cannot distinguish between an empty and a full buffer in a circular arrangement. For the enqueue operation, we first check if the buffer is full based on our counter. If not, we place the new element at the tail index, increment the counter, and update the tail pointer using modulo arithmetic: tail = (tail + 1) % capacity. This ensures that when the tail reaches the end of the array, it seamlessly wraps around to index zero without complex if-else chains. Similarly, dequeue retrieves the element at the head index, increments the counter, and updates the head pointer with the same modulo logic. By maintaining the count, we avoid the ambiguity of head equaling tail. This approach guarantees O(1) time complexity for both operations regardless of buffer size, which aligns with Apple's focus on high-performance, resource-efficient code. Finally, I would discuss potential race conditions in multi-threaded environments and briefly mention mutex locks as a necessary safeguard for production systems.