A tree is an abstract data type that stores elements hierarchically. Each element in a tree has a parent element and zero or more children elements. The top element of the tree is called root.
A tree can also be defined as a set of nodes storing elements in a parent child relationship.
The children nodes of the same parent are called siblings. The node which has children is known as internal. The node which has no children is known as external or leaves.
A free is ordered if there is a linear ordering defined for the chi1dren of each node. e.g, structured documents such as Books.
A binary tree is an ordered tree in which every node has at most two children.
The depth of a node is the number of ancestors of the node excluding the node itself. The depth of the root of a tree is 0.
The height of a tree is equal to the maximum depth of an external node of the tree. The height of the external node is 0.
A traversal of a tree is a systematic way of accessing all the
nodes of the tree. The traversal schemes for trees are preorder and postorder traversals. The root of the tree is visited first in the preorder whereas the children of a tree is visited first in postorder traverse.
The binary tree support a traversal method called inorder traversal.