Avoiding duplication Web Spotify API

I am trying to make a script that synchonise playlists from my website and Spotify with Spotify Web API.

However, I have a problem to avoid duplication: When a user has already created a synchronized playlist and want to update it, I want to make a system that checks the music already imported in spotify and not add them again.

Is there a solution for this? I try with the API by getting every music to test each time, but it is very complicated to have to check the entire playlist for each title that is important.

I thought to suppress the last playlist and created a new one with all music, is this a good idea or not?

Thank you in advance.

Vincent

PS: Sorry for my English a little rough.