Bloomberg Software Developer interview questions

Met with a recruiter during career fair and submitted my resume. Got an email two weeks later to schedule an on telephonic interview. I then scheduled a telephonic interview in which I will be given a link to HackerRankX a code pair website where the interviewer can share the screen with me . It contains a scratch pad an a coding environment. I was given a question on LinkedList. It was flattening a 2D Linked list. The interviewer in the beginning of the interviewer dived into my resume . I mentioned a project on Visual C++ in my resume. He asked me to explain the project . He then asked me the approach for the problem . I fumbled for a bit and gave him the algorithm . He asked me to go ahead and code the algorithm which I mentioned. He was more keen on the edge cases. He just asked me to write the function which takes head as an input parameter. I solved the question in like 20 min and in the rest of the time he explained me the nature of the work at Bloomberg and gave me a chance to ask any questions. Over all the interview went good. Next day I got a mail stating a reject. They did not mention any specific reason for the reject