Basic trees

Let’s start with introducing trees. What are they? Do you have any ideas about how such a data structure should look? If not, let’s take a look at the following diagram, which depicts a tree with captions regarding its particular elements:

Figure 7.1 – Illustration of a tree

A tree consists of multiple nodes, including one root (100 in the diagram). The root does not contain a parent node, while all other nodes do. For example, the parent element of node 1 is 100, while node 96 has node 30 as the parent.

Moreover, each node can have any number of child nodes, such as three children (that is, 50, 1, and 150) in the case of the root. The child nodes of the same node can be named siblings, as in the case of nodes 70 and 61. A node without children is named a leaf, such as 45 and 6 in the diagram.

Let’s take a look at the rectangle with three nodes (that is, 30, 96, and 9). Such a part of the tree can be called...