Is this method of creating a mobile application effective?

Question

Mobile development

In general, the scheme is as follows:
Three sites are created from one database. One for web, second for android, third for iOS. Each site has its own theme.
So the question is, is this method of creating a mobile application effective?

Answer 1

Three sites are being created.

so app or website?? and what does "efficient" mean, what efficiency do you want to achieve, in design, performance, usability, maintenance?