How can I implement a search function to get all trains within a specific route?

Hi I am having difficulty in finding out a way to implement a search function in my app. I am developing a train app where a user could search for available trains between two locations eg: station A to station B. However if a train's route is from station A to station D and when a user searches for a train between station B and station C the above train from station A to station D should be displayed. So based on what criteria can I search the train.

Please give me your valuable advice and suggestions. Thanks in advance !