Tree Traversal Techniques
Last Updated :
23 Jul, 2025
Tree Traversal techniques include various ways to visit all the nodes of the tree. Unlike linear data structures (Array, Linked List, Queues, Stacks, etc) which have only one logical way to traverse them, trees can be traversed in different ways. In this article, we will discuss all the tree traversal techniques along with their uses.
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Tree Traversal
Tree Traversal refers to the process of visiting or accessing each node of the tree exactly once in a certain order. Tree traversal algorithms help us visit and process all the nodes of the tree. Since a tree is not a linear data structure, there can be multiple choices for the next node to be visited. Hence we have many ways to traverse a tree.
There are multiple tree traversal techniques that decide the order in which the nodes of the tree are to be visited. These are defined below:
- Depth First Search or DFS
- Inorder Traversal
- Preorder Traversal
- Postorder Traversal
- Level Order Traversal or Breadth First Search or BFS
Inorder Traversal
Inorder traversal visits the node in the order: Left -> Root -> Right
Algorithm for Inorder Traversal
Inorder(tree )
● Traverse the left subtree, i.e., call Inorder(left->subtree)
● Visit the root.
● Traverse the right subtree, i.e., call Inorder(right->subtree)
Uses of Inorder Traversal
- In the case of binary search trees (BST), Inorder traversal gives nodes in non-decreasing order.
- To get nodes of BST in non-increasing order, a variation of Inorder traversal where Inorder traversal is reversed can be used.
- Inorder traversal can be used to evaluate arithmetic expressions stored in expression trees.
Refer Inorder Traversal of Binary Tree for more
Preorder Traversal
Preorder traversal visits the node in the order: Root -> Left -> Right
Algorithm for Preorder Traversal
Preorder(tree)
● Visit the root.
● Traverse the left subtree, i.e., call Preorder(left->subtree)
● Traverse the right subtree, i.e., call Preorder(right->subtree)
Uses of Preorder Traversal
- Preorder traversal is used to create a copy of the tree.
- Preorder traversal is also used to get prefix expressions on an expression tree.
Refer Preorder Traversal of Binary Tree for more
Postorder Traversal
Postorder traversal visits the node in the order: Left -> Right -> Root
Algorithm for Postorder Traversal:
Postorder(tree)
●Traverse the left subtree, i.e., call Postorder(left->subtree)
● Traverse the right subtree, i.e., call Postorder(right->subtree)
● Visit the root
Uses of Postorder Traversal
- Postorder traversal is used to delete the tree.
- Postorder traversal is also useful to get the postfix expression of an expression tree.
- Postorder traversal can help in garbage collection algorithms, particularly in systems where manual memory management is used.
Refer Postorder Traversal of Binary Tree for more
Level Order Traversal
Level Order Traversal visits all nodes present in the same level completely before visiting the next level.
Algorithm for Level Order Traversal
LevelOrder(tree)
● Create an empty queue Q
● Enqueue the root node of the tree to Q
● Loop while Q is not empty
○Dequeue a node from Q and visit it
○ Enqueue the left child of the dequeued node if it exists
○ Enqueue the right child of the dequeued node if it exists .
Uses of Level Traversal
- Level-wise node processing, like finding maximum/minimum at each level.
- Tree serialization/deserialization for efficient storage and reconstruction.
- Solving problems like calculating the "maximum width of a tree" by processing nodes level by level.
Refer Level Order Traversal (Breadth First Search or BFS) of Binary Tree for more
Other Tree Traversals
- Boundary Traversal
- Diagonal Traversal
1. Boundary Traversal
Boundary Traversal of a Tree includes
- left boundary (nodes on left excluding leaf nodes)
- leaves (consist of only the leaf nodes)
- right boundary (nodes on right excluding leaf nodes)
Refer Boundary Traversal of binary tree for more
2. Diagonal Traversal
In the Diagonal Traversal of a Tree, all the nodes in a single diagonal will be printed one by one.
Refer Diagonal Traversal of Binary Tree for more
Some other important Tutorials:
Tree Traversal
Inorder Traversal of Binary Tree
Pre Order Traversal in Python
Postorder Traversal in Python
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