Interview Series – Raining Numbers

Relevant and Efficient parsing of data from raw files is of utmost importance to generate valuable information.

Here, we’ll see how to parse numbers from a file that are strung together without any delimiters.



We’ll first generate a file containing a large set of consecutive numbers starting from 1. These numbers are present continuously without any delimiters.

The first task is to parse the huge string to store every number as a member of a List of Strings. We’ll go through the concepts of number-lookup, usage of the stream-buffer and declaration of a string containing a repeated character.

Next, we’ll also efficiently parse a file containing numbers without delimiters that aren’t necessarily consecutive. For this, we’ll have certain preconditions set up.

Please check out the 5 video links where I go through this simulated Interview in more detail.


C# Experiments: Raining Numbers (Part 1) 

C# Experiments: Raining Numbers (Part 2) 

C# Experiments: Raining Numbers (Part 3) 

 C# Experiments: Raining Numbers (Part 4) 

C# Experiments: Raining Numbers (Part 5) 

The code typed-in during the interview series is as follows for your reference:-

            //0123456789101112... 20000
            //0,1,2,3,4,5,6,7,8,9,10,11,...,19999,20000

            //using (var sw = new StreamWriter(@"C:\Users\Sandeep\Desktop\numbers.txt"))
            //{
            //    for (int i = 0; i <= 20000; i++)
            //        sw.Write(i);
            //}

            var rainingNumbers = new List<string>();
            var digitBuffer = new Char[10];
            int size = 1;
            string tempStr = null;

            //var numberSizeLookUp = new List<string> { "9", "99", "999", "9999", "99999", "999999", "9999999" };

            //using (var sr = new StreamReader(@"C:\Users\Sandeep\Desktop\numbers.txt"))
            //{
            //    while (!sr.EndOfStream)
            //    {
            //        sr.Read(digitBuffer, 0, size);
            //        //tempStr = new String(digitBuffer, 0, size);
            //        rainingNumbers.Add(new String(digitBuffer, 0, size));

            //        //if (tempStr.Equals(new String('9', size)))
            //        if (rainingNumbers.Last().Equals(numberSizeLookUp[size - 1]))
            //            size++;
            //    }
            //}

            //811179013456798098009981

            //using (var sw = new StreamWriter(@"C:\Users\Sandeep\Desktop\tricky numbers.txt"))
            //{
            //    sw.Write("811179013456798099009981");
            //}

            using (var sr = new StreamReader(@"C:\Users\Sandeep\Desktop\tricky numbers.txt"))
            {
                while (!sr.EndOfStream)
                {
                    sr.Read(digitBuffer, 0, size);
                    tempStr = new String(digitBuffer, 0, size);

                    if (rainingNumbers.Count != 0)
                    {
                        if (Convert.ToDouble(tempStr) <= Convert.ToDouble(rainingNumbers.Last()))
                        {
                            sr.Read(digitBuffer, 0, 1);
                            tempStr = String.Concat(tempStr, new String(digitBuffer, 0, 1));
                            rainingNumbers.Add(tempStr);
                            size++;
                        }
                        else
                            rainingNumbers.Add(tempStr);
                    }
                    else
                        rainingNumbers.Add(tempStr);
                }
            }

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