Amazon Software Development Engineer interview questions

The first round of the interview for the position of SDE for Amazon Services team was a phone interview. The interviewer asked me to join him on Collabaedit, which is an online collaboration tool. First he asked questions about my projects in school and I answered everything. Then he asked to code a problem. He gave me a binary tree and asked me to convert the binary tree into a doubly circular linked list(DCLL). The elements in the DCLL were in an inorder traversal of the tree. I told the logic of how to solve the problem and I coded the problem partially. I made some mistake in coding the problem to perfection. I asked him to ask another question but he said that he is out of time. I was expecting another call from Amazon after this phone interview since it didn't go that bad but they sent me a rejection mail after a week.