C# Program to check whether a node is a LinkedList or not

The Contains() method in C# is used to check whether a specific value exists in a LinkedList<T>. This method searches through all nodes in the LinkedList and returns a boolean value indicating whether the specified element is found.

Syntax

Following is the syntax for using the Contains() method −

public bool Contains(T item)

Parameters

• item − The value to locate in the LinkedList.

Return Value

Returns true if the item is found in the LinkedList; otherwise, false.

Example

Here's how to check whether specific values exist in a LinkedList −

using System;
using System.Collections.Generic;

class Demo {
    static void Main() {
        string[] students = {"Beth", "Jennifer", "Amy", "Vera"};
        LinkedList<string> list = new LinkedList<string>(students);
        
        Console.WriteLine("Original LinkedList:");
        foreach (var stu in list) {
            Console.WriteLine(stu);
        }
        
        // adding a node at the end
        var newNode = list.AddLast("Emma");
        // adding a new node after the node added above
        list.AddAfter(newNode, "Matt");
        
        Console.WriteLine("\nLinkedList after adding new nodes:");
        foreach (var stu in list) {
            Console.WriteLine(stu);
        }
        
        Console.WriteLine("\nChecking if nodes exist:");
        Console.WriteLine("Is Student Amy in the list?: " + list.Contains("Amy"));
        Console.WriteLine("Is Student Anne in the list?: " + list.Contains("Anne"));
        Console.WriteLine("Is Student Matt in the list?: " + list.Contains("Matt"));
    }
}

The output of the above code is −

Original LinkedList:
Beth
Jennifer
Amy
Vera

LinkedList after adding new nodes:
Beth
Jennifer
Amy
Vera
Emma
Matt

Checking if nodes exist:
Is Student Amy in the list?: True
Is Student Anne in the list?: False
Is Student Matt in the list?: True

Using Contains() with Different Data Types

Example

using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        // Integer LinkedList
        LinkedList<int> numbers = new LinkedList<int>();
        numbers.AddLast(10);
        numbers.AddLast(20);
        numbers.AddLast(30);
        
        Console.WriteLine("Number 20 exists: " + numbers.Contains(20));
        Console.WriteLine("Number 25 exists: " + numbers.Contains(25));
        
        // Custom object LinkedList
        LinkedList<string> colors = new LinkedList<string>();
        colors.AddLast("Red");
        colors.AddLast("Green");
        colors.AddLast("Blue");
        
        Console.WriteLine("Color 'Green' exists: " + colors.Contains("Green"));
        Console.WriteLine("Color 'Yellow' exists: " + colors.Contains("Yellow"));
    }
}

The output of the above code is −

Number 20 exists: True
Number 25 exists: False
Color 'Green' exists: True
Color 'Yellow' exists: False

How It Works

The Contains() method performs a linear search through the LinkedList, starting from the first node and comparing each element with the specified value using the default equality comparer. The time complexity is O(n) where n is the number of elements in the LinkedList.

Conclusion

The Contains() method provides a simple way to check if a specific value exists in a LinkedList. It returns a boolean value and works with any data type that the LinkedList contains, making it a versatile tool for searching operations.