SDE - 1

For a given Singly Linked List of integers, sort the list using the 'Merge Sort' algorithm.

You are given a binary tree having 'n' nodes.

The boundary nodes of a binary tree include the nodes from the left and right boundaries and the leaf nodes, each node considered once.

Figure out the boundary nodes of this binary tree in an Anti-Clockwise direction starting from the root node.

Example :

Input: Consider the binary tree A as shown in the figure:

Output: [10, 5, 3, 7, 18, 25, 20]

Explanation: As shown in the figure

The nodes on the left boundary are [10, 5, 3]

The nodes on the right boundary are [10, 20, 25]

The leaf nodes are [3, 7, 18, 25].

Please note that nodes 3 and 25 appear in two places but are considered once.

Reverse a given stack of 'N' integers using recursion. You are required to make changes in the input parameter itself.

Note: You are not allowed to use any extra space other than the internal stack space used due to recursion.

Example:

Input: [1,2,3,4,5] 
Output: [5,4,3,2,1]