C# | Check whether an element is contained in the ArrayList (original) (raw)

Last Updated : 20 Jun, 2022

ArrayList represents an ordered collection of an object that can be indexed individually. It is basically an alternative to an array. It also allows dynamic memory allocation, adding, searching and sorting items in the list. ArrayList.Contains(Object) method determines whether the element exists in ArrayList or not. Properties of ArrayList Class:

Syntax:

public virtual bool Contains (object item);

Here, item is an Object to locate in the ArrayList. The value can be null. Return Value: This method will return True if the item found in the ArrayList otherwise it returns False. Note: This method performs a linear search, therefore, this method is an O(n) operation, where n is Count. Below are the programs to illustrate the ArrayList.Contains(Object) method: Example 1:

CSHARP `

// C# code to check if an element is // contained in ArrayList or not using System; using System.Collections; using System.Collections.Generic;

class GFG {

// Driver code 
public static void Main() 
{ 

    // Creating an ArrayList 
    ArrayList myList = new ArrayList(); 

    // Adding elements to ArrayList 
    myList.Add("A"); 
    myList.Add("B"); 
    myList.Add("C"); 
    myList.Add("D"); 
    myList.Add("E"); 
    myList.Add("F"); 
    myList.Add("G"); 
    myList.Add("H"); 

    // To check if the ArrayList Contains element "E" 
    // If yes, then display it's index, else 
    // display the message 
    if (myList.Contains("E")) 
        Console.WriteLine("Yes, exists at index " + myList.IndexOf("E")); 
    else
        Console.WriteLine("No, doesn't exists"); 
} 

}

`

Output:

Yes, exists at index 4

Example 2 :

CSHARP `

// C# code to check if an element is // contained in ArrayList or not using System; using System.Collections; using System.Collections.Generic;

class GFG {

// Driver code 
public static void Main() 
{ 

    // Creating an ArrayList 
    ArrayList myList = new ArrayList(); 

    // Adding elements to ArrayList 
    myList.Add("5"); 
    myList.Add("7"); 
    myList.Add("9"); 
    myList.Add("11"); 
    myList.Add("12"); 
    myList.Add("16"); 
    myList.Add("20"); 
    myList.Add("25"); 

    // To check if the ArrayList Contains element "24" 
    // If yes, then display it's index, else 
    // display the message 
    if (myList.Contains("24")) 
        Console.WriteLine("Yes, exists at index " + myList.IndexOf("24")); 
    else
        Console.WriteLine("No, doesn't exists"); 
} 

}

`

Output:

No, doesn't exists

Time complexity: O(n) since using Contains method

Auxiliary Space: O(n) where n is the size of the ArrayList

Reference: