Question

The concatenation of two lists can be performed in O(1) time. Which of the following variation of the linked list can be used?

(a) Singly linked list

(b) Doubly linked list

(c) Circular doubly linked list

(d) Array implementation of list

Origin of the question is Singly Linked List Operations in portion Abstract Data Types of Data Structures & Algorithms I

This question was addressed to me in class test.

Answer 1

The correct answer is (c) Circular doubly linked list

Best explanation: We can easily concatenate two lists in O (1) time using singly or doubly linked list, provided that we have a pointer to the last node at least one of the lists. But in case of circular doubly linked lists, we will break the link in both the lists and hook them together. Thus circular doubly linked list concatenates two lists in O (1) time.