Chapter 18: Problem 17

Give pseudocode that implements a queue using two stacks. The queue operations enqueue, dequeue, and empty must be implemented in terms of the \(p u s h, p o p,\) and empty stack operations.

Short Answer

Expert verified

Answer: A queue can be implemented using two stacks (input and output) by performing the following operations: 1. Enqueue: push the item onto the input stack. 2. Dequeue: if the output stack is empty, transfer elements from the input stack to the output stack by popping elements from the input stack and pushing them onto the output stack. Then, pop and return the top element from the output stack. 3. Empty: check if both input and output stacks are empty to determine if the queue is empty.

Step by step solution

Initialize Stacks

Firstly, create two empty stacks - 'input' and 'output'. input = empty stack output = empty stack

Enqueue Operation

To enqueue an element, simply push it onto 'input' stack. enqueue(item): push(item) to the input stack

Dequeue Operation

To dequeue an element, accomplish the following steps: dequeue(): if output stack is empty: while input stack is not empty: pop an element from input stack push that element to output stack if output stack is still empty: return "Queue is empty" else: pop and return the top element from output stack

Empty Operation

Determine if the queue is empty based on the states of the two stacks. empty(): if both input stack and output stack are empty: return True else: return False

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Give pseudocode that implements a queue using two stacks. The queue operations enqueue, dequeue, and empty must be implemented in terms of the \(p u s h, p o p,\) and empty stack operations.

Short Answer

Step by step solution

Initialize Stacks

Enqueue Operation

Dequeue Operation

Empty Operation

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