Types of trees

There are different types of trees, which are explained as follows:

• Binary tree: If the degree of a tree is two, that tree is called a binary tree. For example, the tree shown in the following diagram is a binary tree as it has a degree of two:

Note that the preceding diagram shows a tree that has four levels with eight nodes.

•  Full tree: A full tree is the one in which all of the nodes are of the same degree, which will be equal to the degree of the tree. The following diagram shows the kinds of trees discussed earlier:

Note that the binary tree on the left is not a full tree, as node C has a degree of one and all other nodes have a degree of two. The tree in the middle and the one on the left are both full trees. 

• Perfect tree: A perfect tree is a special type of full tree in which all the leaf nodes are at the same level. For example, the binary tree on the right as shown in the preceding diagram is a perfect, full tree as all the leaf nodes are at the same level, that is, level 2.
• Ordered tree: If the children of a node are organized in some order according to particular criteria, the tree is called an ordered tree. A tree, for example, can be ordered left to right in an ascending order in which the nodes at the same level will increase in value while traversing from left to right.