Usually, they'll pose the task, sit back, and stare at you. You ask a clarifying question, but you know you're stalling for time. The task is clear. You just need to remember the LeetCode solution. The interviewer looks at you impatiently.
You take a stab at describing the solution. You say, "I think this is a job for prefix trees," and look at the interviewer.
The interviewer says, "OK," and gives you a look of alarm and pity.
You solve the problem the way you've solved ten very similar problems on LeetCode. The interviewer says, "Are you sure this works the way you think it does?"
You panic. What did you do wrong?! The interviewer gives you another look of pity.
If you're writing live code, you run it with some test cases. The test cases pass. You think of some edge cases. They pass too. You look at the interviewer. The interviewer says, "OK." A moment elapses.
A few days later the recruiter calls you and extends you a verbal offer. Or they send you an email that says that you won't be getting an offer. The interviewer's expression of pity is the same in either case.