First we discussed the initial approach and the algorithm in whole; I came to one of the possible solutions. The interviewer was well prepared and gave a few hints when I was starting to move in a wrong direction. Then he left the room and let me code for like 10 minutes. I've implemented first half - determining the colors and their numbers, and then he returned to read the code, while I was doing the second part - determining the color positions. I didn't completely finish that, and seems like he was not happy that the second part of the algorithm fulfilled the task, but there was a more simple solution for that part. I think the interviewer considered this task as non-passed.