I believe there have been studies that these types of programming interviews are better at measuring how well someone manages their anxiety rather than filterin

I believe there have been studies that these types of programming interviews are better at measuring how well someone manages their anxiety rather than filtering for technical skills. So don’t feel as though you’re alone there! Even people who are good or decent at these kinds of puzzles will struggle to be successful in an interview situation. That being said it is also possible to manage anxiety. The first step is to master the skill you need to perform until it is nearly subconscious. The less mental effort you can expend on solving the problems the more you have in reserve for regulating your anxiety. The second strategy is to raise your tolerance for feeling anxiety. Don’t interview with the company you want to work at first. Instead prepare interviews with several smaller companies that you’re less interested in and would not be unhappy if they decline to send you an offer. That way you get some practice feeling anxiety without the disappointment or worry about failure. The anxiety won’t go away entirely for nearly anyone. But if you work at it by the time you get to the interview for the job you really want you would be prepared to face the challenge.