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C# Lists & Collections

bookSet Operations and Use Cases

Understanding set operations is essential for many programming tasks. In mathematics, a set is a collection of distinct elements. Sets support special operations based on set theory, such as union, intersection, and difference. In C#, the HashSet<T> class provides these operations through built-in methods.

  • Union combines all unique elements from two sets;
  • Intersection finds elements that are present in both sets;
  • Difference returns elements that are in one set but not the other.

You use these operations to compare or merge data efficiently, making them powerful tools for collection management in C#.

Program.cs

Program.cs

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using System;
using System.Collections.Generic;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            HashSet<string> setA = new HashSet<string> { "apple", "banana", "cherry" };
            HashSet<string> setB = new HashSet<string> { "banana", "date", "elderberry" };

            // Union
            HashSet<string> unionSet = new HashSet<string>(setA);
            unionSet.UnionWith(setB);
            Console.WriteLine("Union:");
            foreach (var item in unionSet)
            {
                Console.WriteLine(item);
            }

            // Intersection
            HashSet<string> intersectionSet = new HashSet<string>(setA);
            intersectionSet.IntersectWith(setB);
            Console.WriteLine("\nIntersection:");
            foreach (var item in intersectionSet)
            {
                Console.WriteLine(item);
            }
        }
    }
}

Set operations are especially useful in many real-world scenarios. You can use sets to remove duplicates from a collection, ensuring that each element appears only once. Sets also help you find common elements between two collections, such as identifying users who appear in two different mailing lists. By leveraging set operations, you can write cleaner and more efficient code to solve these common problems.

Program.cs

Program.cs

copy

              
12345678910111213141516171819202122232425

            
using System;
using System.Collections.Generic;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            HashSet<string> groupA = new HashSet<string> { "Alice", "Bob", "Charlie" };
            HashSet<string> groupB = new HashSet<string> { "Bob", "Diana", "Eve" };

            // Find names in groupA but not in groupB
            HashSet<string> differenceSet = new HashSet<string>(groupA);
            differenceSet.ExceptWith(groupB);

            Console.WriteLine("Names in groupA but not in groupB:");
            foreach (var name in differenceSet)
            {
                Console.WriteLine(name);
            }
        }
    }
}

1. What does the IntersectWith method do?

2. When would you use a set instead of a list?

3. Fill in the blanks to find unique elements in two HashSet<int>:

question mark

What does the IntersectWith method do?

Select the correct answer

question mark

When would you use a set instead of a list?

Select the correct answer

question-icon

Fill in the blanks to find unique elements in two HashSet<int>:

HashSet set1 = new HashSet { 1, 2, 3, 4 };HashSet set2 = new HashSet { 3, 4, 5, 6 };// Find elements in set1 but not in set2HashSet unique = new HashSet(set1);(set2);foreach (var num in unique){ Console.WriteLine(num);}
1
2

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Thanks for your feedback!

SectionΒ 3. ChapterΒ 2

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bookSet Operations and Use Cases

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Understanding set operations is essential for many programming tasks. In mathematics, a set is a collection of distinct elements. Sets support special operations based on set theory, such as union, intersection, and difference. In C#, the HashSet<T> class provides these operations through built-in methods.

  • Union combines all unique elements from two sets;
  • Intersection finds elements that are present in both sets;
  • Difference returns elements that are in one set but not the other.

You use these operations to compare or merge data efficiently, making them powerful tools for collection management in C#.

Program.cs

Program.cs

copy

              
123456789101112131415161718192021222324252627282930313233

            
using System;
using System.Collections.Generic;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            HashSet<string> setA = new HashSet<string> { "apple", "banana", "cherry" };
            HashSet<string> setB = new HashSet<string> { "banana", "date", "elderberry" };

            // Union
            HashSet<string> unionSet = new HashSet<string>(setA);
            unionSet.UnionWith(setB);
            Console.WriteLine("Union:");
            foreach (var item in unionSet)
            {
                Console.WriteLine(item);
            }

            // Intersection
            HashSet<string> intersectionSet = new HashSet<string>(setA);
            intersectionSet.IntersectWith(setB);
            Console.WriteLine("\nIntersection:");
            foreach (var item in intersectionSet)
            {
                Console.WriteLine(item);
            }
        }
    }
}

Set operations are especially useful in many real-world scenarios. You can use sets to remove duplicates from a collection, ensuring that each element appears only once. Sets also help you find common elements between two collections, such as identifying users who appear in two different mailing lists. By leveraging set operations, you can write cleaner and more efficient code to solve these common problems.

Program.cs

Program.cs

copy

              
12345678910111213141516171819202122232425

            
using System;
using System.Collections.Generic;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            HashSet<string> groupA = new HashSet<string> { "Alice", "Bob", "Charlie" };
            HashSet<string> groupB = new HashSet<string> { "Bob", "Diana", "Eve" };

            // Find names in groupA but not in groupB
            HashSet<string> differenceSet = new HashSet<string>(groupA);
            differenceSet.ExceptWith(groupB);

            Console.WriteLine("Names in groupA but not in groupB:");
            foreach (var name in differenceSet)
            {
                Console.WriteLine(name);
            }
        }
    }
}

1. What does the IntersectWith method do?

2. When would you use a set instead of a list?

3. Fill in the blanks to find unique elements in two HashSet<int>:

question mark

What does the IntersectWith method do?

Select the correct answer

question mark

When would you use a set instead of a list?

Select the correct answer

question-icon

Fill in the blanks to find unique elements in two HashSet<int>:

HashSet set1 = new HashSet { 1, 2, 3, 4 };HashSet set2 = new HashSet { 3, 4, 5, 6 };// Find elements in set1 but not in set2HashSet unique = new HashSet(set1);(set2);foreach (var num in unique){ Console.WriteLine(num);}
1
2

Click or drag`n`drop items and fill in the blanks

Everything was clear?

How can we improve it?

Thanks for your feedback!

SectionΒ 3. ChapterΒ 2
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