A graph is a finite and nonempty set of vertices and edges. A directed graph is a graph whose edges have a direction associated with them. A directed acyclic graph is a directed graph with no cycles in it. A tree is a directed acyclic graph that satisfies three more principles: firstly, it has a root node: the entry point to the tree; secondly, every vertex, except the root, has one and only one entry point; and thirdly, there is a path that connects the root with each vertex and belongs to the tree.
As a result, the root is the first node of the tree. Each node can be connected to one or more nodes depending on the tree type. If each node leads to one and only one other node, then the tree is a linked list!
The most commonly used type of tree is called a binary tree because each node can have up to two children. The following figure shows a graphical representation...
