There are three kinds of candidates who fail software engineering interviews for technical reasons.

There are those that don’t know how to write code. Sorry but that’s a requirement for software engineering jobs.

There are those that can write code but are unable to come up with good ideas to solve the given problems. Difficult to judge why this goes wrong. Maybe just a bad interview.

There is a third kind of candidate that is particularly maddening to watch. Those are the candidates that propose great solutions and write confident and skilled code. However, the code they write doesn’t match their proposed solution at all. They might propose a perfect solution using a tree and breadth-first search but then write code that uses a binary search over a linked list.

Candidates of the third category are a rare breed but I see them often enough to wonder. How is it possible for evidently experienced and talented candidates not to see the complete disconnect between their proposed solutions and their implemented solutions? Is it just the nerves?