From Quora(Why we get rejected even if we have solved the problem)

(I’ve conducted over 100 interviews for Google but, to be clear, the rest of this answer refers to possible explanations, not necessarily anything I’ve experienced.)

Some possible reasons that the candidate might think they “solved the problem right” but didn’t get the call include:

• The candidate thought they’d solved the problem, but there was some major flaw in their solution that we didn’t have time to discuss, so I didn’t point it out.
• The candidate had solved the problem, but their solution was really bad (e.g. it is logically correct but runs in O(2^n) when an O(n) solution exists), and again, there was no time left to improve it.
• The candidate had solved the problem, but it was a really basic problem that was meant to be an ice-breaker that fills 5–10 minutes but actually took the whole interview.
• The candidate had solved the problem, but only after getting a lot of hints that reduced the problem to a simple “fill in the blanks” exercise.
• The candidate had some other major culture fit problem, like being extremely rude, or lying on their CV.