1. I got a bit tangled on this and took up lots of time. Got something working but missed an edge case 2. I described a solution to this immediately and should probably have coded it up - but I wasted lots of time discussing with the interviewer. I had heard that it's best to avoid writing code before having got the go-ahead from the interviewer which I followed to the letter. In my case this was the wrong thing to do because I described a solution but the interviewer was very back-foot and was just silent when I asked if I should start coding