smart pointer

[zhtdavis]

when I am doing the second part of the assignment. I notice that if I use

const std::shared_ptr node = q.top().second; (create a copy of the smart pointer). Everything will correct and the brute force and tree search match.

But if I switch to const std::shared_ptr& node = q.top().second; (create a reference to the smart pointer)

The result no longer matches.

Is it some special property of smarter pointer?