What are the latest methods to train a chat bot? I would like to train a bot that uses text input, memorizes a few categories and answers questions accordingly. In addition as version 2.0, I want to make the bot to answer voice inputs as well. Which are the latest machine learning/AI algorithms available for the same? Please let me know.
Your question is incredibly broad -- so in response, two broad frameworks I'd encourage you to look at are:


For cutting edge chatbot conversation development http://rasa.ai is an open source framework that is more adaptable than more traditional rule-based systems
For speech recognition check out https://discourse.mozilla.org/c/deep-speech that is also open source.