Pre, Post and In order traversal of binary trees

## DESCRIPTION

Pre-order :- 
visit the root node
traverse the left sub-tree
traverse the right sub-tree
 In-order :- 
traverse the left sub-tree
 visit the root node
 traverse the left sub-tree
 Post-order :- 
traverse the left sub-tree
traverse the right sub-tree
 visit the root node


## EXPECTED OUTCOME

all nodes of tree should be traversed.





