Amazon Placement Paper

Amazon->written test.
They concentrate on every field of computer science. They asked c,data structure,TOC(context free and context sensitive grammar,regular languages). DBMS unix was not there.
There were two subjective questions.
1. The first one was "given two lists write a function which returns a list which is the intersection of the two lists.the original lists should remain same. (Intersection - if first list is say,1,20 3,45 and second list is 3,24 ,45,90,68 then intersection should be 3,45 )
2. The second was given two nodes of a binary tree find the closest ancestor of the two nodes.
Note:consider binary tree and binary search tree also.
In short answer type questions, the questions were -
1.There was an aptitude's question in which P(A) and P(B) were given and we had to find P(B/A) and P(A/B) when A and B are independent events.
2.What is the probability that the the 4 digit's no. which is formed by using the digits 1,2,3,4,5,6 is divisible by 4.
3.What tree traversal gives the no. in sorted order.Inorder,preorder or postorder ?
4.Preorder and inorder traversal was given and we had to find the tree.
5. Which sorting algorithm takes best and worst time complexity as O(nlogn)?
6.A dbms query was asked to find the second largest no. of book sold.(i don't remember the question exactly)