Winter Roads

MST is only 1k nodes, so most operations are cheap. S is just a bfs in O(n), R is similar...bfs from the two endpoints of the repaired road (if not on the tree) and swap out if the repaired edge is higher than the min on that path in O(n).

B is harder, but max 2k B operations, so can rebuild the MST each time. Don't rebuild the heap in kruskal, so you don't eat the extra log...just update the heap for each B and R. Only rebuild if B operation is for an edge on the current MST.