QTREE - Edge Update

Each edge $i$ connects two nodes $(u, v)$. Store a mapping edge_to_node[i] that tells you which node stores edge $i$. This is the child node in the parent-child pair. When you read edge $i$ with endpoints $(u, v)$, determine which is the parent using depth or parent array.

Store edge $i$ at the child node. To update edge $i$ to $ti$, find v = edge_to_node[i] and update pos[v] in the segment tree to $ti$. This is a single point update.