(Tree|Nested Set|Hierarchy) Data Structure

About

A tree is a node that may have children. Tree's are inherently recursive by definition as each child of a node is a Tree itself, with or without children nodes.

A tree is a special case of a graph structure as this is the only graph that have a hierarchical relationship.

It's an rooted acyclic undirected graph. Undirected because the relation between a parent and its child is symmetric.

Relationship rules:

A tree is a data structures with no or slow random access. Tree structure scale well.

A set of tree is known as a forest.

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