An Introduction to Trees and Basic Tree Properties

In this chapter, we are going to study the basics of the tree data structure!


Trees consist of vertices (nodes) and edges that connect them. Unlike the linear data structures that we have studied so far, trees are hierarchical. They are similar to Graphs, except that a cycle cannot exist in a Tree - they are acyclic. In other words, there is always exactly one path between any two nodes.

  • Root Node: A node with no parent nodes.
  • Child Node: A Node that is linked to an upper node (Parent Node).
  • Parent Nodes: A Node that has links to one or more child nodes.
  • Sibling Node: Nodes that share the same Parent Node.
  • Leaf Node: A node that doesn’t have any Child Nodes.
  • Ancestor Nodes: the nodes on the path from a node d to the root node. Ancestor nodes include node d’s parents, grandparents, and so on.

The figure below shows all the terminologies described above:

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