That's definitely the way to go. If you try to "remember" an answer you read or even previously completed while in an interview there's a good chance you won't instantly recall the answer and often the problem is slightly adjusted from your first encounter. It makes it difficult to see the problem with new eyes http://lesswrong.com/lw/k7/original_seeing/

There are some serious benefits to bringing up your prior exposure to a question in a positive light. When sending out problems interviewees are likely to encounter again I include the group's "déjà vu guide" http://codingforinterviews.com/seen-question-before