These are some LCA (lowest common ancestor) problems. I hope you enjoy them.
I tried to sort them by difficulty. If you know more problems, add it to comments.
208E - Blood Cousins
191C - Fools and Roads
519E - A and B and Lecture Rooms
587C - Duff in the Army
609E - Minimum spanning tree for each edge
178B3 - Greedy Merchants
176E - Archaeology
466E - Information Graph