static void GetCharCountArray(string str)
 {
     for (int i = 0; i < str.Length; i++)
     {
         if (hm.ContainsKey(str[i]))
         {
             hm[str[i]].IncreaseCount();
         }
         else
         {
             hm[str[i]] = new CountIndex(i);
         }
     }
 }
            /* calculate count of characters
             * in the passed string */
            public static void getCharCountArray(string str)
            {
                for (int i = 0; i < str.Length; i++)
                {
                    // If character already occurred,
                    if (hm.ContainsKey(str[i]))
                    {
                        // updating count
                        hm[str[i]].incCount();
                    }

                    // If it's first occurrence, then
                    // store the index and count = 1
                    else
                    {
                        hm[str[i]] = new CountIndex(i);
                    }
                }
            }