anujparikh / linkedlist

LinkedList Data Structure

Introduction

A linked list is a linear data structure, in which the elements are not stored at contiguous memory locations. The elements in a linked list are linked using pointers. In simple words, a linked list consists of nodes where each node contains a data field and a reference(link) to the next node in the list

• A linked list is represented by a pointer to the first node of the linked list. The first node is called the head
• If the linked list is empty, then the value of the head is NULL

Advantages of Linked List over Arrays

• Dynamic Size
• Ease of insertion/deletion

Drawbacks

• Random access is not allowed. We have to access elements sequentially starting from the first node
• Extra memory space for a pointer is required with each element of the list
• Not cache friendly. Since array elements are contiguous locations, there is locality of reference which is not there in case of linked lists.

Best use-case

• Excessive read, as time complexity of read is always O(1)
• Random access to element using index

Time Complexity for Array (average and worst-case)

• Access: O(n)
• Search: O(n)
• Insertion: O(1)
• Deletion: O(1)

Time Complexity for Linked List java class (worst-case)

• add(): O(1)
• get(): O(n)
• remove(): O(1)
• contains(): O(n)

Methods in java.util.LinkedList Class

Methods	Description	Returns	Notes
add(index i, Element e)	This method Inserts the specified element at the specified position in this list	void
add(Element e)	This method appends the specified element to the end of this list	boolean	This method returns True after execution
addAll​(int index, Collection c)	This method Inserts all of the elements in the specified collection into this list, starting at the specified position	boolean
addFirst​(E e)	This method Inserts the specified element at the beginning of this list	void
addLast​(E e)	This method Appends the specified element to the end of this list	void
contains​(Object o)	This method returns true if this list contains the specified element	boolean
fill	Assigns the specified value to each element of the specified range of the specified array	void
sort	Sorts the specified array into ascending numerical order	void

• Other methods includes clear, clone, get(index i), indexOf(Object o), toArray()

Common syntaxs

• Initializing LinkedList in java

LinkedList<String> object = new LinkedList<String>();

Examples

• Delete Node from Linked List (without head): Solution (Easy)
• Remove Nth Node From End of List: Solution (Easy)
• Reverse Linked List: Solution (Easy)
• Merge Two Sorted Lists: Solution (Easy)
• Palindrome Linked List: Solution (Easy)
• Linked List Cycle: Solution (Easy)
• Add Two Numbers: Solution (Medium)
• Odd Even Linked List: Solution (Medium)
• Intersection of Two Linked Lists: Solution (Medium)