Given is graph with networks and bridges/switches. We know, the root Bridge is the bridge with the minimal Bridge-ID. The connections between every bridge and network is 1.
In the lecture slides they calculated the "best"(shortest) path from one network to the root bridge. I assume they used BFS, because it would be the easiest way to calculate the shortest path, but if they used BFS, why is the algorithm called Spanning-Tree-Algorithm?