Depth first search is a graph search algorithm that starts at one node and uses recursion to travel as deeply down a path of neighboring nodes as possible, before coming back up and trying other paths.
I think that in the video the explore callback should be called outside of the function itself right (one line lower). It’s correct in the sandbox :). Great course by the way!
Yeah Haroen Viaene was right. Video should be changed or should be given a tip in the video itself.