The problem with leetcode is that it selects people who practiced leetcode and rejects people who did not but would potentially be better engineers. It's the problem of any metrics: people will optimize for the metric.

If you try to answer with an LLM, you'll have to copy-paste the question (or write it), wait for an answer, read the answer, understand it, correct it (because most likely it won't be 100% correct), and answer to your interviewer, all while pretending you are not doing that.

You may as well Google the question and try to find an already-existing answer while pretending you are not doing that, right?

My feeling is that the interviewer will quickly realise what you are doing.