Stack in C#

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

A stack represents a variable size last-in-first-out (LIFO) collection of instances of the same specified type.

Three main operations can be performed on a stack and its elements: <ul><li>Push inserts an element at the top of the Stack.</li> <li>Pop removes an element from the top of the Stack.</li> <li>Peek returns an element that is at the top of the Stack but does not remove it from the Stack.<li> </ul> <h4>Creating a Stack</h4> <p>We create a Stack in C# using the following syntax:
Stack<T> st = new Stack<T>();
<T> here denotes any datatype which we want to create a stack of.

Properties of Stack

• Count: This property gets the number of elements present in the stack.

Methods of Stack

• Push(T): Inserts an object at the top of the Stack.</li>
• Pop(): Removes and returns the object at the top of the Stack.</li>
• Peek(): Returns the object at the top of the Stack without removing it.</li>
• Contains(T): Determines whether an element is in the Stack.</li>
• Clear(): Removes all objects from the Stack.</li> </ul>

  ---

  Stack Operation Examples:

  Different Stack operations are demonstrated in the example below:

  using System;
  using System.Collections.Generic;
  namespace StackDemo {
      class Example {
          static void Main(string[] args) {
              Stack  st = new Stack ();
              st.Push(5);          
              st.Push(5);
              st.Push(2);
              st.Push(9);
              
              Console.WriteLine(st.Count);        // Prints 4, the size of stack
              
              Console.WriteLine(st.Peek());       // Prints 9, the top element
              
              Console.WriteLine(st.Pop());       // Prints 9, then removes it
              Console.WriteLine(st.Pop());       // Prints 2, then removes it
              
              Console.WriteLine(st.Contains(5));  // Checks if 5 is present
              Console.WriteLine(st.Contains(2));  // Checks if 2 is present
          }
      }
  }
  </code></pre>
  Output: 
  4
  
  9
  
  9
  
  2
  
  True
  
  False
  
  
  Task
  In the editor below, perform the different tasks as directed.