Given a binary tree, the task is to flatten it in order of its post-order traversal. In the flattened binary tree, the left node of all the nodes must be NULL.
Input: 5 / \ 3 7 / \ / \ 2 4 6 8 Output: 2 4 3 6 8 7 5 Input: 1 \ 2 \ 3 \ 4 \ 5 Output: 5 4 3 2 1
A simple approach will be to recreate the Binary Tree from its post-order traversal. This will take O(N) extra space were N is the number of nodes in BST.
A better solution is to simulate post-order traversal of the given binary tree.
- Create a dummy node.
- Create variable called ‘prev’ and make it point to the dummy node.
- Perform post-order traversal and at each step.
- Set prev -> right = curr
- Set prev -> left = NULL
- Set prev = curr
This will improve the space complexity to O(H) in the worst case as post-order traversal takes O(H) extra space.
Below is the implementation of the above approach:
2 4 3 6 8 7 5
- Flatten Binary Tree in order of Level Order Traversal
- Flatten Binary Tree in order of Zig Zag traversal
- Find n-th node in Postorder traversal of a Binary Tree
- Postorder traversal of Binary Tree without recursion and without stack
- Print a Binary Tree in Vertical Order | Set 3 (Using Level Order Traversal)
- Given level order traversal of a Binary Tree, check if the Tree is a Min-Heap
- Density of Binary Tree using Level Order Traversal
- Perfect Binary Tree Specific Level Order Traversal
- Perfect Binary Tree Specific Level Order Traversal | Set 2
- Find the kth node in vertical order traversal of a Binary Tree
- Calculate height of Binary Tree using Inorder and Level Order Traversal
- Check if the level order traversal of a Binary Tree results in a palindrome
- Check if the given array can represent Level Order Traversal of Binary Search Tree
- Create a binary tree from post order traversal and leaf node array
- Build Binary Tree from BST such that it's level order traversal prints sorted data
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.