Top-nodes Algorithm - Principle

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.

Example of a 7-hour calendar (with elementary periods of one hour)

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.
Top-nodes for a reservation from 1:00 to 5:59

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

Famous quotes containing the word principle:

    The first principle of a free society is an untrammeled flow of words in an open forum.
    Adlai Stevenson (1900–1965)

    To light one candle to God and another to the Devil is the principle of wisdom.
    José Bergamín (1895–1983)

    Whether our feet are compressed in iron shoes, our faces hidden with veils and masks; whether yoked with cows to draw the plow through its furrows, or classed with idiots, lunatics and criminals in the laws and constitutions of the State, the principle is the same; for the humiliations of the spirit are as real as the visible badges of servitude.
    Elizabeth Cady Stanton (1815–1902)