BFS and DFS in Data Structure | Inorder, Preorder and Postorder Traversal with practical example.

Article by: Manish Methani

Last Updated: October 9, 2021 at 10:04am IST
1 min 30 sec read

Depth first Search (DFS) is used to traverse a tree in any of following three ways listed below :

1) Inorder Traversal (Left - Root - Right)
2) Preorder Traversal (Root - Left- Right)
3) Postorder Traversal (Left - Right - Root)

Consider the following example for better visual illustration

DFS of given tree,

1) Inorder Traversal :-  4 2 5 1 3 6
2) Preorder Traversal :- 1 2 4 5 3 6
3) Postorder Traversal :- 4 5 2 6 3 1

While traversing a tree you should divide parts into Left, Root, and Right which makes work easier while traversing. If tree contains more levels again divide them into Left-Root-Right. Then you can apply the DFS traversal with any of given three golden rules.

Remember Golden Rules of DFS Traversal:-

1) Inorder traversal (Left - Root - Right)
2) Preorder traversal (Root - Left- Right)
3) Postorder traversal (Left - Right - Root)

2) Breadth First Traversal(BFS)

Breadth First Traversal is also called Level Order Traversal in which you have to traverse level by level from root node.

BFS of given tree is 1 2 3 4 5 6