I coded the first use-case had to also write all getter and setter methods(I believe these can be eliminated), the interviewer was very patient and even helped me with one typo. As soon as I was done with it, we faced a couple coder pad issues and he helped me through it., as I ran the test case, he then said oh it also expects some additional requirement. I added that.. then moved to next method.. he again gave me basic outline - I implemented that and when ran the test case, he explained it needs these additional things as well.. I had to change the whole data structure that I had used cause the use case demanded completely different results.. Then i switched my data structure, made the code changes again, we saw one of the test case was failing.. I had considered multiple cases but one of the factor was missing and it lead to empty result and we ran out of time. The interviewer was very nice and helpful but the code pad, the problem length and the description of the problem could have been better. The same problem if the definition is clear can definitely be solved in given time.