3rd phone interview with Amazon

I thought after the second interview, and in fact I was told, that I would go to Seattle for the next interview. When I called the recruiter, she said that they want to have a third phone interview. I don't appreciate them changing their word, but all I could do is play along. The ball is in their court. So on the third phone interview, the questions got a lot harder, and where ones that I hadn't encountered before. Here where the questions.

1. If you are given a set of 1000 integers in a set A , and 10,000,000 integers in a set B, how would you create a set C that would only contain numbers that are both in A and B?

2. In a general tree, how would you find the lowest common ancestor of two nodes that are given to you as parameters?

3. If you are given a number as a parameter, write a function that would put commas after every third digit from the right.

4. How would you do a design of a monopoly game (later changed to a chess game)?

I felt that the first two questions where unreasonable for a phone screen, especially since they had already asked me technical and coding questions to test my ability in the first two phone screens. I didn't do so well on this third phone screen, and I am not expecting to be invited to seattle for a regular interview. They are just being real hard asses about selecting someone for this position, and almost being unreasonable with their expectations. I feel that at the end they are gonna feel desperate at crunch time and decide to hire the first person that happens to apply for the position at the right time. I will write answers to the technical questions above in a later post.