I have partipated successfully in a number of competitions. Some thoughts:
Know what the interviewers are looking for. Generally speaking, interviewers are not looking for your technical knowledge, that should have been demonstrated in the context of your previous study and in written portions of the competition (if any). Rather, they are likely to be looking for your ability to communicate orally, your ability to respond in an interactive process, your ability to incorporate new information into your reasoning process, and your general "fit" with an organizational culture.
That being said, strengthen those areas in which you are weak--practice by doing mock interviews with colleagues, by reciting material in front of a mirror, etc.
Give some thought to seeking accommodation. If you disclose to a potential employer that you have a disability that requires extra time or extra consideration in an interview situation, it might work in your interests. Using the opportunity to educate your interviewers about your strengths and weaknesses may provide you with an opportunity to develop a level of self-awareness that your peers lack.
Many NTs at your age and stage believe that they can do anything. By telling inteviewers, "I know what I can do, and I know what I can't do," you distinguish yourself from the pack.
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--James