[zeroonetwothree]

Maybe he would have been a poor fit at Google. Just because you wrote some popular open source software doesn't mean you will succeed in a corporate environment. The dynamics and skills required are quite different.

Now does being able to reverse a binary tree mean that you would fail at Google? I have no idea. But we don't really know if that was the reason he was rejected, it's just his own guess. There could have been other reasons.