Reverse Anti Clockwise Spiral Traversal of a Binary Tree
Given a binary tree, the task is to print the nodes of the tree in a reverse anti-clockwise spiral manner.
Input : 1 / \ 2 3 / \ \ 4 5 6 / / \ 7 8 9 Output : 7 8 9 1 4 5 6 3 2 Input : 20 / \ 8 22 / \ / \ 5 3 4 25 / \ 10 14 Output : 10 14 20 5 3 4 25 22 8
Approach: The idea is to use two variables i initialized to 1 and j initialized to the height of tree and run a while loop which wont break until i becomes greater than j. We will use another variable flag and initialize it to 1. Now in the while loop we will check a condition that if flag is equal to 1 we will traverse the tree from left to right and mark flag as 0 so that next time we traverse the tree from right to left and then decrement the value of j so that next time we visit the level just above the current level. Also when we will traverse the level from top we will mark flag as 1 so that next time we traverse the tree from left to right and then increment the value of i so that next time we visit the level just below the current level. Repeat the whole process until the binary tree is completely traversed.
Below is the implementation of the above approach:
10 14 20 5 3 4 25 22 8
Time Complexity: O(N^2), where N is the total number of nodes in the binary tree.
Auxiliary Space: O(N)