Amazon Intern interview questions

Given an array of size 2n+1 where n integers repeat two times and one integer occured only once, Find that integer. I told him by using XOR. then he changed the question to Given an array of size 2n+2 where n integers repeat 2 times and 2 integers come only once. Find both of them.

Given any binary tree in which all the leaves had their left and right pointers connected in a doubly linked list from left to right instead of pointing to NULL. Also, the leftmost leaf’s left pointer pointed to that node itself and the rightmost leaf’s right pointer pointed to that leaf itself and if there was an internal node with no left or right child, that particular pointer will point to that node itself.

4. He asked me about the data structures I knew and then started asking questions on Graphs. How we represent them? which is better Adjacency matrix or List?

Replace the data of every node of a Binary Search Tree with the sum of all the nodes greater than it.