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Stack<T> and Queue<T> in C# – Different Real-Time Examples

1. Stack<T> – Browser Back Navigation

Scenario: A web browser maintains a history of visited pages. When the user clicks the Back button, the most recently visited page is retrieved first.

Stack<string> browserHistory = new();

browserHistory.Push("Google");
browserHistory.Push("YouTube");
browserHistory.Push("GitHub");
browserHistory.Push("LinkedIn");

// Current page
Console.WriteLine(browserHistory.Peek());

// Go back
browserHistory.Pop();

Console.WriteLine(browserHistory.Peek());

Output:

LinkedIn
GitHub

Execution flow:

Browser History (LIFO)

      ┌──────────────┐
TOP → │ LinkedIn     │ ← Current Page
      ├──────────────┤
      │ GitHub       │
      ├──────────────┤
      │ YouTube      │
      ├──────────────┤
      │ Google       │
      └──────────────┘

Back Button → Pop()

LinkedIn removed
GitHub becomes current page

Key points:

Push() adds a visited page.
Pop() removes the current page from the stack.
Peek() retrieves the current page without removing it.
Stack follows LIFO.

2. Queue<T> – Printer Job Processing

Scenario: Multiple employees send documents to a printer. The printer processes jobs in the order they were received.

Queue<string> printJobs = new();

printJobs.Enqueue("Invoice.pdf");
printJobs.Enqueue("Report.pdf");
printJobs.Enqueue("Salary.pdf");
printJobs.Enqueue("Receipt.pdf");

while (printJobs.Count > 0)
{
    string document = printJobs.Dequeue();

    Console.WriteLine($"Printing: {document}");
}

Output:

Printing: Invoice.pdf
Printing: Report.pdf
Printing: Salary.pdf
Printing: Receipt.pdf

Execution flow:

Printer Queue (FIFO)

FRONT                               REAR
  ↓                                  ↓
┌─────────┬────────┬────────┬─────────┐
│ Invoice │ Report │ Salary │ Receipt │
└─────────┴────────┴────────┴─────────┘
    ↓                            ↑
 Dequeue()                    Enqueue()

First received → First printed

Key points:

Enqueue() adds a print job.
Dequeue() removes the oldest pending job.
Peek() checks the next job without removing it.
Queue follows FIFO.

3. Quick Interview Comparison

Scenario	Collection	Reason
Browser back navigation	`Stack<T>`	Last visited page first
Recursive backtracking	`Stack<T>`	Last saved state first
Printer job processing	`Queue<T>`	First submitted job first
Customer support tickets	`Queue<T>`	First received ticket first
Breadth-first search (BFS)	`Queue<T>`	Processes nodes in FIFO order
Depth-first search (DFS)	`Stack<T>`	Processes most recently added node first

Interview tip: Use Stack<T> when the most recently added item must be processed first. Use Queue<T> when items must be processed in their arrival order.

Stack<T> and Queue<T> in C#

Stack<T> and Queue<T> in C# – Different Real-Time Examples

1. Stack<T> – Browser Back Navigation

2. Queue<T> – Printer Job Processing

3. Quick Interview Comparison

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