C# Stack, Queue and HashSet

Besides List and Dictionary, C# has a Stack (last in, first out), a Queue (first in, first out) and a HashSet (unique values).

ExampleC#

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Stack<int> stack = new Stack<int>();
        stack.Push(1);
        stack.Push(2);
        stack.Push(3);
        Console.WriteLine(stack.Pop());
        Console.WriteLine(stack.Peek());

        Queue<string> queue = new Queue<string>();
        queue.Enqueue("first");
        queue.Enqueue("second");
        Console.WriteLine(queue.Dequeue());
        Console.WriteLine(queue.Count);

        HashSet<int> set = new HashSet<int> { 3, 1, 3, 2, 1 };
        Console.WriteLine(set.Count);
        Console.WriteLine(set.Contains(2));
    }
}

Output

3
2
first
1
3
True

Quick check

Which collection returns the most recently added item first?

StackQueueHashSet

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

Tip: use the left and right arrow keys to move between lessons.