Solution3.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 

namespace cSharpSolutions
{
    internal class Solution3
    {
        private class Stack<T>
        {
            private T[] _items;
            private int _count;
            private int _capacity;

            public Stack(int initialCapacity = 4)
            {
                _capacity = initialCapacity;
                _items = new T[_capacity];
                _count = 0;
            }

            public void Push(T item)
            {
                if (_count == _capacity)
                {
                    _capacity *= 2;
                    Array.Resize(ref _items, _capacity);
                }

                _items[_count++] = item;
            }

            public T Pop()
            {
                if (IsEmpty())
                    throw new InvalidOperationException("Stack is empty.");

                _count--;
                T item = _items[_count];
                _items[_count] = default!; // clear slot for GC
                return item;
            }

            public T Peek()
            {
                if (IsEmpty())
                    throw new InvalidOperationException("Stack is empty.");
                return _items[_count - 1];
            }

            public bool IsEmpty() => _count == 0;

            public int Count() => _count;
        }

        public static void Run()
        {
            Console.WriteLine("=== Solution 3: Stack Implementation ===");

            var stack = new Stack<int>();
            stack.Push(1);
            stack.Push(2);
            stack.Push(3);

            Console.WriteLine($"Stack count: {stack.Count()}");
            Console.WriteLine($"Top element (peek): {stack.Peek()}");

            Console.WriteLine("Popping elements:");
            while (!stack.IsEmpty())
                Console.WriteLine(stack.Pop());

            Console.WriteLine($"Stack empty? {stack.IsEmpty()}");
            Console.WriteLine("\nSolution 3 complete");
        }
    }
}