addFirst linked list c

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The LinkedList generic class in the System.Collections.Generic namespace provides the AddFirst[] method, which can be used to add a node at the start of the linked list in C#.

Syntax

• The method takes the value T as input and returns a new LinkedListNode containing the passed input value.

• The method has an overload available that takes LinkedListNode as input and adds it to the start of the list.

Things to note

• This method is an O[1] operation.

• LinkedList accepts null as a valid reference type value.

• LinkedList allows duplicate values as well.

• For an empty linked list, the new node becomes the First and the Last node.

In the below code, we created a linked list of strings named monthList and added the names of the months to it. The linked list contains three strings: March, April, and May.

using System; using System.Collections.Generic; class LinkedListAddition { static void Main[] { LinkedList monthList = new LinkedList[]; monthList.AddLast["March"]; monthList.AddLast["April"]; monthList.AddLast["May"]; Console.WriteLine["LinkedList Elements"]; Print[monthList]; monthList.AddFirst["February"]; Console.WriteLine["LinkedList Elements After AddFirst['February']"]; Print[monthList]; monthList.AddFirst["January"]; Console.WriteLine["LinkedList Elements After AddFirst['January']"]; Print[monthList]; } private static void Print[LinkedList list] { foreach [var node in list] { Console.Write[node + ", "]; } Console.WriteLine["\n"]; } }

We call the AddFirst[] method by passing February as the argument on this linked list. We can see that the first node is shown as February in the output.

We again call the AddFirst[] method by passing January as the argument. We can see that the first node is shown as January in the output.

We created a helper method, Print[], to display the linked list nodes.

The LinkedList class is maintained internally as a doubly-linked list, and AddFirst[] is an O[1] operation.

• Type Parameters:E - the type of elements held in this collection All Implemented Interfaces: Serializable, Cloneable, Iterable, Collection, Deque, List, Queue
  public class LinkedList extends AbstractSequentialList implements List, Deque, Cloneable, Serializable

  Doubly-linked list implementation of the List and Deque interfaces. Implements all optional list operations, and permits all elements [including null].

  All of the operations perform as could be expected for a doubly-linked list. Operations that index into the list will traverse the list from the beginning or the end, whichever is closer to the specified index.

  Note that this implementation is not synchronized. If multiple threads access a linked list concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally. [A structural modification is any operation that adds or deletes one or more elements; merely setting the value of an element is not a structural modification.] This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no such object exists, the list should be "wrapped" using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list:

  List list = Collections.synchronizedList[new LinkedList[...]];

  The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the Iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

  Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

  This class is a member of the Java Collections Framework.

  Since: 1.2 See Also:List, ArrayList, Serialized Form

• • • equals, hashCode, listIterator, removeRange, subList
    • containsAll, isEmpty, removeAll, retainAll, toString
    • finalize, getClass, notify, notifyAll, wait, wait, wait

• • • public LinkedList[]

      Constructs an empty list.

    • public LinkedList[Collection