Objective: – Given a binary tree, Do the reverse level order traversal. In our earlier post we have seen normal Level Order Traversal. In reverse level order traversal we first need to print the last level followed by second last level up to the root, which is the first level.
Example:
Approach: Use Stack
- Use the Queue and do the level order traversal, read “Level Order Traversal” First if you doesn’t know the technique.
- Instead of printing the Node, keep adding it to Stack.
- At the End print all the nodes from Stack, it will be in reverse order than normal level order traversal.
Code:
Output:
7 6 5 4 3 2 1
should’nt the output be like this
4 5 6 7 2 3 1
queue insertion order needs to be changed. First insert right child and then left child
Reverse level order means that we will print the last level first and then from there we will go to the root. It does not matter actually whether in a particular level which node you insert first, left or right.
It does matter for the order in which you insert the node into stack. The nodes should always be printed from left to right