C++ Navigation Path Distance

Thanks for reading.

How can I find the distance of an AI’s current path to it’s target? In C++.

For example, I have an area filled with walls and doors. I’d like to be able to find locations within a certain range from the player that take into account NOT going through these walls.

Any information about using navigation from C++ would be very useful as well.

I have a few ideas for doing this manually but I’d just like to know if I can leverage the UE4 api instead.

This looks great.
Had no idea it existed.
Thanks very much.