Wait. I fail to understand why this counts as a reason for rejection. You attempted a solution, which the interviewer backed up (I assume if you were heading in a completely incorrect direction, he would have told you that), you showed quick thinking (connecting local maximas to the problem) as well as coding competence and basic testing knowledge.
Is this not what Twitter desires through its interviews?Because time and again I have heard that companies look and focus on people's thought processes more than their exact results.
PS: I'm a college student so I'm really keen to know how important being 100% accurate is.