> A 49 years old java programmer even complained that the test isn’t fair because it’s stressful to program in front of people, so now I take the habit of sitting in the next room
Whether programmers like it or not, live coding has become a standard for interviews these days. I can see anyone still unfamiliar with this doing poorly, I used to do awful at these until I realized this is just part of the game, but it's not unreasonable to expect candidates to be able to do whiteboard/live coding.
However, you just sitting in the other room, tells me you also have a lot to learn about the structure of live coding interviews. Every major Big Co. that does these has a very well established flow, including providing helpful clues to the candidate. Most companies provide training to all interviewers to make sure this process is smooth, repeatable and fair to candidates.
Common tips are to: first make sure the candidate understands the question, make sure they are thinking out loud the entire time. You don't let the candidate go too far down the wrong path. Most important you have a list of anticipated questions with stock answers to help stuck candidates, as well as a list of stock prompts to help them get on the right track if they are lost.
For example, in your challenge, if a candidate is stuck you might ask as simpler subproblem "so how would you find out if a sting contained the letter 'a'?" and if a candidate starts heading down the wrong path, prompt with "hmmm... I think I see where you're going, but I recommend you back up a bit and rethink this part here"
It sounds like you're in a small shop so I highly recommend you enlist a few friends (especially some that have done interviewing at large companies) to help you work out the kinks in the interview itself.
Whether programmers like it or not, live coding has become a standard for interviews these days. I can see anyone still unfamiliar with this doing poorly, I used to do awful at these until I realized this is just part of the game, but it's not unreasonable to expect candidates to be able to do whiteboard/live coding.
However, you just sitting in the other room, tells me you also have a lot to learn about the structure of live coding interviews. Every major Big Co. that does these has a very well established flow, including providing helpful clues to the candidate. Most companies provide training to all interviewers to make sure this process is smooth, repeatable and fair to candidates.
Common tips are to: first make sure the candidate understands the question, make sure they are thinking out loud the entire time. You don't let the candidate go too far down the wrong path. Most important you have a list of anticipated questions with stock answers to help stuck candidates, as well as a list of stock prompts to help them get on the right track if they are lost.
For example, in your challenge, if a candidate is stuck you might ask as simpler subproblem "so how would you find out if a sting contained the letter 'a'?" and if a candidate starts heading down the wrong path, prompt with "hmmm... I think I see where you're going, but I recommend you back up a bit and rethink this part here"
It sounds like you're in a small shop so I highly recommend you enlist a few friends (especially some that have done interviewing at large companies) to help you work out the kinks in the interview itself.