This is why I place a lot of value in the feedback during the interview. While it's important that they come up with a working solution, it's their behaviour that determines whether that will happen.
I will often have people who could not solve the problem on their own, but by listening to their thoughts and reading their code, I can guide them towards a working solution. This fulfills the requirements I think you want: can this person learn and grow.
Well said, thank you for the reply.
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