using System.Collections.Generic;

using System;

using System.Text;

​

namespace TextAnalysis

{

    static class SentencesParserTask

    {

        public static List<List<string>> ParseSentences(string text)

        {   

            var sentencesList = new List<List<string>>();

            var sentences = text.Split('.', '!', '?', ';', ':', '(', ')');

            foreach (var sentence in sentences)

            {

                var parsedSentence = Parse(sentence);

                if (parsedSentence.Count > 0)

                    sentencesList.Add(parsedSentence);

            }  

            return sentencesList;

        }

        public static List<string> Parse(string sentence)

        {

            var word = new StringBuilder();

            var wordsList = new List<string>();

            foreach (var character in sentence)

            {

                if ((char.IsLetter(character)) || (character == '\''))

                    word.Append(character);

                else 

                {

                    if (word.Length > 0)

                        wordsList.Add(word.ToString().ToLower());

                    word.Clear();

                }

            }

            if (word.Length != 0)

                wordsList.Add(word.ToString().ToLower());

            return wordsList;

        }

    }

}

​

​