Stack.cs

using System;
using System.Collections.Generic;

namespace Code.StackDS;

/// <summary>
/// Stack data structure.
/// </summary>
/// <typeparam name="T"></typeparam>
public class Stack<T>
{
    private List<T> items;

    /// <summary>
    /// Constructor to initialize the stack.
    /// </summary>
    /// <param name="data"></param>
    public Stack()
    {
        items = [];
    }

    /// <summary>
    /// Add an element to the stack.
    /// </summary>
    /// <param name="data"></param>
    public void Push(T data)
    {
        items.Add(data);
    }

    /// <summary>
    /// Remove and return the top element from the stack.
    /// </summary>
    /// <returns></returns>
    /// <exception cref="InvalidOperationException"></exception>
    public T Pop()
    {
        if (items.Count == 0)
        {
            throw new InvalidOperationException("Stack is empty.");
        }
        var item = items[^1];
        items.RemoveAt(items.Count - 1);
        return item;
    }

    /// <summary>
    /// Return the top element from the stack without removing it.
    /// </summary>
    /// <returns></returns>
    /// <exception cref="InvalidOperationException"></exception>
    public T Peek()
    {
        if (items.Count == 0)
        {
            throw new InvalidOperationException("Stack is empty.");
        }
        return items[^1];
    }
 
    public bool IsEmpty => items.Count == 0;
    public int Count => items.Count;
    public List<T> Items => items;
}