Chapter 18: Problem 16

What problem is overcome by using a circular array for a static queue?

Short Answer

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**Answer:** Using a circular array for a static queue overcomes the problem of unused spaces at the beginning of the array. With the circular array implementation, when the rear pointer reaches the end of the array, it loops back to the start, filling any available space if the front pointer has moved forward. This way, the entire array is efficiently used, and enqueue operations can continue as long as there are empty spaces in the array. It can be implemented by modifying the enqueue and dequeue operations using the modulo operator, allowing the front and rear pointers to wrap around the array.

Step by step solution

Understanding Static Queues

In a static queue, the queue is implemented using a fixed-size array. The front and rear pointers indicate the first and last elements in the queue respectively. When elements are dequeued, the front pointer moves forward, creating empty spaces at the beginning of the array, which aren't reused. As a result, when dequeuing and enqueuing occur repeatedly, the rear pointer reaches the end of the array, and the queue is considered full even if there are empty spaces at the beginning of the array.

Introducing Circular Arrays

A circular array allows us to treat the array as if it wraps around in a circle. In a circular array, when the end of the array is reached, and there are still empty spaces at the beginning of the array, the pointers wrap around to the start, reusing these empty spaces. This technique helps to manage memory efficiently and avoids wasted space.

Overcoming the Problem in Static Queues

Using a circular array for a static queue overcomes the problem of unused spaces at the beginning of the array. With the circular array implementation, when the rear pointer reaches the end of the array, it loops back to the start, filling any available space if the front pointer has moved forward. This way, the entire array is efficiently used, and enqueue operations can continue as long as there are empty spaces in the array.

Implementation Example

To implement a circular array for a static queue, we can modify the enqueue and dequeue operations using the modulo operator. For example, let's assume we have an array 'arr' of size 'n', and front and rear pointers 'f' and 'r' respectively: - Enqueue operation: 1. Check if the queue is full (if (r + 1) \% n == f). 2. If not full, enqueue the element: arr[r] = element. 3. Update rear pointer: r = (r + 1) \% n. - Dequeue operation: 1. Check if the queue is empty (if f == r). 2. If not empty, dequeue the front element: element = arr[f]. 3. Update front pointer: f = (f + 1) \% n. Using this implementation, we can efficiently manage memory and avoid wasted spaces in the array.

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What problem is overcome by using a circular array for a static queue?

Short Answer

Step by step solution

Understanding Static Queues

Introducing Circular Arrays

Overcoming the Problem in Static Queues

Implementation Example

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