Sets in C#

In this article, we will learn about the sets in C#.

A set is a collection that contains no duplicate elements.

There are two types of sets in C# under the System.Collections.Generic namespace.
<ul><li>HashSet</li><li>SortedSet</li></ul>

HashSet does not store the elements in order while giving faster operation time.
SortedSet stores the elements in order which allows more functionality.

Creating a Set

We create a HashSet / SortedSet in C# using the following syntax:
HashSet<T> l1 = new HashSet<T>();
SortedSet<T> l1 = new SortedSet<T>();
<T> here denotes any datatype of which we want to create a list of.

Properties of Sets

• Count: This property gets the number of elements actually contained in the set.
• Comparer: Determines equality for the values in the set.
• Max: Gets the maximum value in the set, as defined by the comparer. (only for SortedSet)
• Min: Gets the maximum value in the set, as defined by the comparer. (only for SortedSet)

Methods of Sets

• Add(T): Adds the element to the set.
• Clear(): Removes all the elements from the set.
• Contains(T): Determines whether a value is in the set.
• Remove(T): Removes the element from the set.

Set Operation Examples:

Different Set operations are demonstrated in the example below:

using System;
using System.Collections.Generic;
namespace SetDemo {
    class Example {
        static void Main(string[] args) {
            HashSet < int > HS = new HashSet < int > ();
            HS.Add(5);          
            HS.Add(5);          
            HS.Add(2);
            HS.Add(9);
            Console.WriteLine(HS.Count);        // Prints 3 because 5 is only added once in the set
            
            Console.WriteLine(HS.Contains(5));  // Checks if 5 is present
            
            HS.Remove(5);                       // Removes 5
            
            Console.WriteLine(HS.Contains(5));  // Prints False this time
            
            SortedSet < int > SS = new SortedSet < int > ();
            SS.Add(5);          
            SS.Add(5);          
            SS.Add(2);
            SS.Add(9);
            Console.WriteLine(SS.Max);   // Prints the maximum element in the set
            
            Console.WriteLine(SS.Min);   // Prints the minimum element in the set
            foreach(int i in SS) {
                Console.Write(i + " ");
            }
            Console.WriteLine();
        }
    }
}

Output:

3

True

False

9

2

2 5 9

Task

In the editor below, perform the different tasks as directed.