A queue is implemented using an array such that ENQUEUE and DEQUEUE op...
We can use circular array to implement both in O(1) time. See below article for details.
- Queue Introduction and Array Implementation
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A queue is implemented using an array such that ENQUEUE and DEQUEUE op...
Queue Implementation using Array
A queue is a data structure that follows the FIFO (First In First Out) principle, where the first element that is inserted into the queue will be the first one to be removed. A queue can be implemented using an array or a linked list.
Array Implementation of Queue
In an array implementation of a queue, we maintain a front and a rear pointer. The front pointer points to the first element of the queue, and the rear pointer points to the last element of the queue. Initially, both front and rear are set to -1.
ENQUEUE Operation
When an item is to be inserted into the queue, we increment the rear pointer and insert the item at the position pointed by the rear pointer. If the rear pointer reaches the end of the array and there is still space for insertion, we wrap around the rear pointer to the beginning of the array.
DEQUEUE Operation
When an item is to be removed from the queue, we increment the front pointer and return the item at the position pointed by the front pointer. If the front pointer reaches the end of the array, we wrap around the front pointer to the beginning of the array.
Efficient ENQUEUE and DEQUEUE Operations
To perform both ENQUEUE and DEQUEUE operations efficiently, we need to avoid shifting the elements of the array every time an item is inserted or removed. Instead, we can maintain a count variable that keeps track of the number of items in the queue. This count variable can be used to determine whether the queue is empty or full.
If the queue is not full, we can insert an item at the position pointed by the rear pointer and increment the rear pointer. If the queue is not empty, we can remove an item from the position pointed by the front pointer and increment the front pointer.
Answer
Option A is correct: Both operations can be performed in O(1) time.
Explanation:
When we maintain a count variable to keep track of the number of items in the queue, we can perform both ENQUEUE and DEQUEUE operations in O(1) time, regardless of the number of items in the queue.
- ENQUEUE Operation: If the queue is not full, we can insert an item at the position pointed by the rear pointer and increment the rear pointer. This operation takes O(1) time because we are not shifting any elements of the array.
- DEQUEUE Operation: If the queue is not empty, we can remove an item from the position pointed by the front pointer and increment the front pointer. This operation takes O(1) time because we are not shifting any elements of the array.
Therefore, both ENQUEUE and DEQUEUE operations can be performed efficiently in O(1) time.
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