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

namespace ReverseSentence
{
    class Program
    {
        static void Main(string[] args)
        {
            var sentence = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.".ToCharArray();
            var sentenceLength = sentence.Length;
            var sentenceMax = sentence.Length -1;
            var reversedSentence = new char[sentenceLength];
            var writeIndex = sentenceMax;
            var wordLength = 0;

            for (int i = 0; i < sentenceLength; i++)
            {
                if(i == sentenceMax)
                {
                    writeIndex -= wordLength - 1;
                    Array.Copy(sentence, i - wordLength, reversedSentence, writeIndex, wordLength);

                    writeIndex--;
                    reversedSentence[writeIndex] = sentence[i];
                    break;
                }

                switch (sentence[i])
                {
                    case ' ':
                    case ',':
                    case '.':
                    {
                        writeIndex -= wordLength -1;

                        Array.Copy(sentence, i - wordLength, reversedSentence, writeIndex, wordLength);

                        writeIndex--;
                        reversedSentence[writeIndex] = sentence[i];

                        writeIndex--;
                        wordLength = 0;

                        break;
                    }

                    default:
                    {
                        wordLength++;
                        break;
                    }
                }
            }

            Console.WriteLine($"sentence: {new string(sentence)}");
            Console.WriteLine($"sentence: {new string(reversedSentence)}");

            Console.ReadLine();
        }
    }
}