Q1 has four elements and Q2 has none (Initial State). Only operations: Enqueue(Q,element) and Dequeu

Q: What is GATE-CS?

GATE-CS is a competitive examination conducted in India. This question is from the 2022 GATE-CS Data Structures paper.

Q: How can I prepare for GATE-CS Data Structures?

To prepare for GATE-CS Data Structures, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2022 question covers Queues topic.

Q: What is the difficulty level of this question?

This GATE-CS 2022 Data Structures question has a hard difficulty level.

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You can find more GATE-CS previous year questions on AspirantMitraa. Browse by subject, topic, year, and difficulty level to practice effectively.

Question

Q1 has four elements and Q2 has none (Initial State). Only operations: Enqueue(Q,element) and Dequeue(Q). Place elements of Q1 in Q2 in reverse order (Final State) without additional storage. Minimum number of Enqueue operations on Q1 required is ___

Accepted Answer

Answer: 0Concept -- Queue Reversal without Extra Storage (from Cormen et al., Introduction to Algorithms):Q1 = [a, b, c, d] (front to back). We want Q2 = [d, c, b, a]. Only Enqueue and Dequeue operations are available, using Q1 and Q2 only (no additional storage).Strategy: Use Q2 itself as temporary storage. Dequeue from Q1 and enqueue to Q2 repeatedly, rotating Q2 to build the reversed order. The minimum number of ENQUEUE OPERATIONS ON Q1 (not on Q2) is 0 -- we never need to enqueue anything back onto Q1. We only dequeue from Q1 and enqueue onto Q2. All elements move one-way from Q1 to Q2 with rotations within Q2.The question asks specifically for 'Enqueue operations on Q1'. If we use Q2 as buffer and rotate within Q2 by dequeuing from Q2 and enqueuing to Q2, we never need to enqueue back to Q1. Minimum Enqueue on Q1 = 0.

Q1 has four elements and Q2 has none (Initial State). Only operations: Enqueue(Q,element) and Dequeue(Q). Place elements of Q1 in Q2 in reverse order (Final State) without additional storage. Minimum number of Enqueue operations on Q1 required is ___

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Q1 has four elements and Q2 has none (Initial State). Only operations: Enqueue(Q,element) and Dequeue(Q). Place elements of Q1 in Q2 in reverse order (Final State) without additional storage. Minimum number of Enqueue operations on Q1 required is ___

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