I need some machine learning algorithms

I'm working on an AI chatbot that uses machine learning, and I have a few ideas. Which do you think would work best/do you have any other ideas? (1) Trial & error: It has a list of common phrases, and tries each one against your input to see if it would make sense. (2) It starts with very basic, hardcoded responses, then whenever you say something to it, it just adds it as a response to whatever the AI said before hand. (3) Interview method: It finds online interviews, and searches for somebody in an interview saying what the user inputted. Then, it replies with whatever the other person in the interview replied with.