Explain and comment the C# code below line by line? Also, include running and space complexity for the code.

using System; using System.Collections; using System.IO; namespace ConsoleApp1 {

class Program { static void Main(string[] args) {

if (!File.Exists("input.txt")) { Console.WriteLine("Input file not found"); } else { Console.WriteLine("Reading input.txt..."); string[] lines = File.ReadAllLines("input.txt");

Stack stack = new Stack();

foreach (var line in lines) { stack.Push(line); }

int i = 0;

while (stack.Count != 0) { lines[i] = (string)stack.Pop(); i++; }

Console.WriteLine("Writing reverse text to output.txt..."); File.WriteAllLines("output.txt", lines); }

}

}

}