Count word practice - C# practice on August 7, 2017 12:00 pm, it took 40 minutes, failed to run the code because of the bug in first writing

countWord_practice.cs

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

namespace SplitStringAndSort
{
    class Program
    {
        /// <summary>
        /// count word practice - August 7, 2017
        /// 
        /// </summary>
        /// <param name="args"></param>
        static void Main(string[] args)
        {
            var result = CountWordPractice("this practice is good one. Good to practice."); 
        }

        public static string[,] CountWordPractice(string document)
        {
            // your code goes here
            if (document == null || document.Length == 0)
            {
                return new string[0, 2];
            }

            var delimiter = new char[] { '.', '!', ' ' };
            var split = document.Split(delimiter);

            var dictionary = addToDictionary(split);

            // bucket sort 
            var size = dictionary.Values.Max(); // LINQ 
            var sorted = new List<string[]>[size];   // 0 - max value, ..., size -1 - 1
            var total = dictionary.Count; // 
            foreach (var pair in dictionary)
            {
                var key = pair.Key;
                var value = pair.Value;

                int index = size - value;
                if(sorted[index] == null)
                {
                    sorted[index] = new List<string[]>(); // added after the practice
                }

                sorted[index].Add(new string[] { key, value.ToString() });
            }

            // output to two dimension array 
            var result = new string[total, 2];
            var row = 0;  // added aftr the mocking - bug in writing 
            for (int i = 0; i < size; i++)
            {
                var visit = sorted[i]; // visit is List<string[]>
                foreach (var item in visit) // add the loop after the mocking ... bug in writing
                {
                    result[row, 0] = item[0]; // visit[0] is the array, string new List<string[]>[size]
                    result[row, 1] = item[1];
                    row++; 
                }
            }

            return result;
        }

        private static Dictionary<string, int> addToDictionary(string[] items)
        {
            var result = new Dictionary<string, int>();

            foreach (var item in items)
            {
                var key = filter(item); // you'll -> youll
                if (result.ContainsKey(key))
                {
                    result[key]++;
                }
                else
                {
                    result.Add(key, 1);
                }
            }

            return result;
        }

        private static string filter(string s)
        {
            //var filterString = "abc'"; 
            var filtered = new StringBuilder();

            foreach (var item in s)
            {
                if (item != '\'')
                {
                    filtered.Append(item);
                }
            }

            return filtered.ToString();
        }
    }
}