Principle
The calendar is stored as a binary tree where leafs represent elementary time periods. Other nodes represent the period of time covered by all their descendants.
The period of time covered by a reservation is represented by a set of "top-nodes". This set is the minimal set of nodes that exactly cover the reservation period of time.
A node of the binary tree is a "top-node" for a given reservation if
- all its descendants are inside the reservation period of time,
and
- it is the root node, or at least one descendant of the parent node is outside of the reservation period of time.
The following value is stored in each node:
q(node) = max(q(left child), q(right child)) + total amount of reserved resource for all reservations having this node as a "top-node"(for code optimization, the two parts of this sum are usually stored separately.)
Read more about this topic: Top-nodes Algorithm
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