Tree Queries

This problem can be solved with BIT or Merge Sort Tree after constructing the required array using DFS (topological sort). The main observation is that for a node $L$ it's range for the given query is $L+sub\_tree\_size[L]$. and you can get the exact node's order by doing a topological sort in the tree.

Then you can do basic merge sort tree to find the answer where the time complexity is $Q \times log^2(n)$ or you can do it with BIT where the time complexity is $Q \times log(n)$.