# GATE Questions & Answers of Queues

## What is the Weightage of Queues in GATE Exam?

Total 7 Questions have been asked from Queues topic of Programming and Data Structures subject in previous GATE papers. Average marks 1.57.

A queue is implemented using a non-circular singly linked list. The queue has a head pointer and a tail pointer, as shown in the figure. Let n denote the number of nodes in the queue. Let enqueue be implemented by inserting a new node at the head, and dequeue be implemented by deletion of a node from the tail.
Which one of the following is the time complexity of the most time-efficient implementation of enqueue and dequeue, respectively, for this data structure?

A circular queue has been implemented using a singly linked list where each node consist of a value and a single pointer pointing to the next node. We maintain exactly two external pointers FRONT and REAR pointing to the front node and rear node of the queue, respectively. Which of the following statement is/ are CORRECT for such a circular queue, so that insertion and deletion operations can be performed in (1) time?

I. Next pointer of front node point to the rear node.

II. Next pointer of rear node points to the front node.

A queue is implemented using an array such that ENQUEUE and DEQUEUE operations are performed efficiently. Which one of the following statements is CORRECT (n refers to the number of items in the queue)?

Let Q denote a queue containing sixteen numbers and S be an empty stack. Head(Q) returns the element at the head of the queue Q without removing it from Q. Similarly Top(S) returns the element at the top of S without removing it from S. Consider the algorithm given below.

The maximum possible number of iterations of the while loop in the algorithm is____________ .

Suppose a stack implementation supports an instruction REVERSE, which reverses the order of elements on the stack, in addition to the PUSH and POP instructions. Which one of the following statements is TRUE with respect to this modified stack?

Consider the following operation along with Enqueue and Dequeue operations on queues, where k is a global parameter.
MultiDequeue(Q){
m = k
while (Q is not empty) and (m > 0) {
Dequeue(Q)
m = m – 1
}
}

What is the worst case time complexity of a sequence of n queue operations on an initially empty queue?