An important class of digraph, which involves for the description of hierarchy. A directed tree is an acyclic digraph which has one node called *root* with in degree 0, while other nodes have in degree Every directed tree must have at least one node.

An isolated node is also called as directed tree. The node with out degree as 0 is called as leaf. The length of the path from root to particular node level of the node. If the ordering of the node at each level is prescribed then the tree is called as ordered tree.

## Binary Tree

** **If a tree has at most of two children, then such tree is called as Binary tree. If the elements in the binary tree are arranged in the following order

**Left element is lesser than the root**

** Right element is greater then the root**

** No duplication of elements**

Then such binary tree is called as** Binary Search Tree**

** **

**Operations performed in a binary tree are:**

** **

- Inserting a node
- Deleting a node
- Traversing the tree

**Traversing Methods**

** **

**1. **Pre – order method

**2. **In – order method

**3. **Post – order method

**4. **Converse Pre – order method

**5. **Converse In – order method

**6. **Converse post – order method

Pre – order method

** **This method gives the tree key value in the following manner: –

1. Process the root

2. Traverse the left sub tree

3. Traverse the right Sub tree

In – order method

** **This method gives the tree key value in the following manner: –

1. Traverse the left sub tree

2. Process the root

3. Traverse the right Sub tree

Post – order method

** **This method gives the tree key value in the following manner: –

1. Traverse the left sub tree

2. Traverse the right Sub tree

3. Process the root