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How to remove a node from the start of a linked list in C#

Surabhi Sharma

The LinkedList<T> generic class in the System.Collections.Generic namespace provides the RemoveFirst() method, which can remove a node from the start of a linked list in C#.

The LinkedList<T> class in C# is internally implemented as a doubly-linked list, with insertion and removal as O(1) operations.

The illustration below shows how the RemoveFirst() method works for a linked list of strings.

Syntax

public void RemoveFirst ();

Parameters

This method does not take any parameters.

Return value

This method does not return anything.

Things to note

  • This method is an O(1) operation.
  • RemoveFirst throws an InvalidOperationException if the LinkedList<T> object does not have any nodes.

Code

The code below demonstrates the use of the RemoveFirst() method.

using System;
using System.Collections.Generic;

class LinkedListRemover
{
    static void Main()
    {
        LinkedList<string> monthList = new LinkedList<string>();
        monthList.AddLast("January");
        monthList.AddLast("February");
        monthList.AddLast("March");
        monthList.AddLast("April");
        monthList.AddLast("May");
        monthList.AddLast("June");

        Console.WriteLine("LinkedList Elements");
        Print(monthList);

        monthList.RemoveFirst();
        Console.WriteLine("LinkedList Elements After RemoveFirst()");
        Print(monthList);

        monthList.RemoveFirst();
        Console.WriteLine("LinkedList Elements After RemoveFirst()");
        Print(monthList);
    }

    private static void Print(LinkedList<string> list)
    { 
        foreach (var node in list)
        {
            Console.Write(node + ", ");
        }
        Console.WriteLine("\n");        
    }
}

Explanation

  • In the code above, we create a linked list of strings and add the names of a few months. The linked list contains six strings - "January", "February", "March", "April", "May", and "June".

  • We also create a helper method, Print(), to display the linked list nodes.

  • We call the RemoveFirst() method on the linked list and it removes the node from the start of the list. We can see that the first node, "January", is removed in the output.

  • We call the RemoveFirst() method again and print all the nodes. We can observe that the first element, "February", is also removed from the list and is not present in the output.

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