Find index of multiple keywords in given text file

Question

I want to find the index/offset of a batch of keywords in a given text file. Now, I've come across many questions on stackoverflow but answer this one fits the best for me.

The only issue here is that above questions provide a solution for only a single keyword while I have more than 25 keywords to find & i think there has to be a better solution than to write switch...case or if...else for each keyword.

How can I optimize my task here? Any better approach other than the linked question is also welcome.

Let'say my text file has following content:

Stephen Haren,December,9,4055551235

Laura Clausing,January,23,4054447788

William Connor,December,13,123456789

Kara Marie,October,23,1593574862

Audrey Carrit,January,16,1684527548

Sebastian Baker,October,23,9184569876

And keywords i want to find are :

December, January, March, April, May

Now, the output should be:

December : 16

January : Overall Index of January in line 2

December : Overall Index of January in line 3

....

Current code:

class Program
    {
        static void Main(string[] args)
        {
            var keyword = "December";
            var keyword2 = "January";
            int totalLength = 0;
            using (var sr = new StreamReader("file.txt"))
            {
                while (!sr.EndOfStream)
                {
                    var line = sr.ReadLine();
                    if (String.IsNullOrEmpty(line)) continue;
                    if (line.IndexOf(keyword, StringComparison.CurrentCultureIgnoreCase) >= 0)
                    {
                        Console.WriteLine("December: " + (totalLength + line.IndexOf(keyword, StringComparison.CurrentCultureIgnoreCase)));
                    }
                    if (line.IndexOf(keyword2, StringComparison.CurrentCultureIgnoreCase) >= 0)
                    {
                        Console.WriteLine("January: " + (totalLength + line.IndexOf(keyword, StringComparison.CurrentCultureIgnoreCase)));
                    }
                    .................
                  ........................................................

                    totalLength += line.Length;
                }

            }
        }
    }

Note: Tagging Java here too as I am interested in approach rather than language-specific solution.

Please add to your question your inputs and expected outputs. Also, what did you try so far? Post your code. — Dave, Mar 08 '19 at 08:09
One approach is to convert the data of .txt file in to a datatable and then run query on the table with the search parameters. — Chetan, Mar 08 '19 at 08:17
https://stackoverflow.com/questions/1050112/how-to-read-a-csv-file-into-a-net-datatable — Chetan, Mar 08 '19 at 08:18
What is the value associated with this: `December : 16`? What is the number 16? — Dave, Mar 08 '19 at 08:35
@ChetanRanpariya Thanks for the approach but my guess is that the sql query for that will kill the performance not to mention that i'll need to create another table to save the keywords which won't be possible. — Harshil Doshi, Mar 08 '19 at 08:44
https://social.msdn.microsoft.com/Forums/en-US/1434177b-461f-430e-ab48-9c0ba1f52c0b/run-sql-query-on-datatable?forum=adodotnetdataset — Chetan, Mar 08 '19 at 08:54

Eric McLachlan · Answer 1 · 2019-03-08T18:35:05.700

I would definitely suggest you check out a Trie data structure.

A good implementation of Tries will search the input text character-by-character and returns whenever it reaches the end of a recognized word. It's extremely efficient i.t.o. runtime (approx O(n + m)) and not bad when it comes to memory consumption either. (FYI: In this case, n is the length of the input text and m is the length of the word you're looking for).

I found the following tutorial on the subject:

https://www.geeksforgeeks.org/trie-insert-and-search/

And here is a good implementation I found via StackOverflow:

http://www.glennslayden.com/code/c-sharp/trie

Find index of multiple keywords in given text file

1 Answers1