Find the last node in LinkedList containing the specified value in C#

The FindLast() method in C# LinkedList is used to find the last occurrence of a node containing the specified value. This method searches from the end of the LinkedList towards the beginning and returns the last LinkedListNode<T> that contains the specified value.

Syntax

Following is the syntax for the FindLast() method −

public LinkedListNode<T> FindLast(T value)

Parameters

• value − The value to locate in the LinkedList.

Return Value

Returns the last LinkedListNode<T> that contains the specified value, or null if the value is not found.

Using FindLast() with Integer Values

The following example demonstrates finding the last occurrence of a duplicate value in a LinkedList of integers −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      LinkedList<int> list = new LinkedList<int>();
      list.AddLast(100);
      list.AddLast(200);
      list.AddLast(300);
      list.AddLast(400);
      list.AddLast(500);
      list.AddLast(300);
      list.AddLast(500);
      
      Console.WriteLine("LinkedList elements...");
      foreach(int i in list) {
         Console.WriteLine(i);
      }
      
      LinkedListNode<int> val = list.FindLast(300);
      Console.WriteLine("Specified value = " + val.Value);
   }
}

The output of the above code is −

LinkedList elements...
100
200
300
400
500
300
500
Specified value = 300

Using FindLast() with String Values

The following example shows how to use FindLast() with string values −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      LinkedList<string> list = new LinkedList<string>();
      list.AddLast("One");
      list.AddLast("Two");
      list.AddLast("Three");
      list.AddLast("Four");
      list.AddLast("Five");
      
      Console.WriteLine("Elements in LinkedList...");
      foreach (string res in list) {
         Console.WriteLine(res);
      }
      
      LinkedListNode<string> val = list.FindLast("Five");
      Console.WriteLine("Specified value = " + val.Value);
   }
}

The output of the above code is −

Elements in LinkedList...
One
Two
Three
Four
Five
Specified value = Five

Handling Non-Existent Values

When searching for a value that doesn't exist, FindLast() returns null. Here's how to handle this scenario −

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      LinkedList<int> list = new LinkedList<int>();
      list.AddLast(10);
      list.AddLast(20);
      list.AddLast(30);
      
      LinkedListNode<int> found = list.FindLast(99);
      if (found != null) {
         Console.WriteLine("Found value: " + found.Value);
      } else {
         Console.WriteLine("Value 99 not found in the LinkedList");
      }
      
      LinkedListNode<int> existing = list.FindLast(20);
      Console.WriteLine("Found existing value: " + existing.Value);
   }
}

The output of the above code is −

Value 99 not found in the LinkedList
Found existing value: 20

Conclusion

The FindLast() method is essential for locating the last occurrence of a specific value in a LinkedList. It returns the actual LinkedListNode<T> containing the value, or null if not found, making it useful for navigation and manipulation operations within the LinkedList structure.