SDE - 1

How much coffee of variety A, costing Rs. 5 a kg should be added to 20 kg of Type B coffee at Rs. 12 a kg so that the cost of the two coffee variety mixture be worth Rs. 7 a kg?

You have been given a Binary Search Tree of integers. You are supposed to convert it to a greater sum tree such that the value of every node in the given BST is replaced with the sum of the values of all the nodes which are greater than the value of the current node in the tree.

A Binary Search Tree is a tree, whose internal nodes each store a value greater than all the values in the node's left subtree and less than those in its right subtree.

Note :

You need to modify the given tree only. You are not allowed to create a new tree.

For example:

For the given binary search tree

11 will be replaced by {15 + 29 + 35 + 40}, i.e. 119.
2 will be replaced by {7 + 11 + 15 + 29 + 35 + 40}, i.e. 137.
29 will be replaced by {35 + 40}, i.e. 75.
1 will be replaced by {2 + 7 + 11 + 15 + 29 + 35 + 40}, i.e. 139.
7 will be replaced by {11 + 15 + 29 + 35 + 40}, i.e. 130.
15 will be replaced by {15 + 29 + 35 + 40}, i.e. 104.
40 will be replaced by 0 {as there is no node with a value greater than 40}.
35 will be replaced by {40}, i.e. 40.

You live in a Ninja town which is in the form of a N * M grid. In this town, people travel from one place to another by jumping over the buildings which are present in each cell of the grid. It is Christmas eve, and Santa wants to give gifts and chocolates to the kids who live in the building which is present at the cell (N - 1, M - 1). Initially, Santa is present on cell (0, 0). Since Santa is in a hurry, help him find a path from starting point to the endpoint with the least amount of time.

The Santa may go only from one building to any of its adjacent buildings which is present either to the right or to the bottom or bottom right cell i.e. if the current position is (x, y), he may go to (x + 1, y + 1) or (x + 1, y) or (x, y + 1) given that the new coordinates are in the grid. The time taken to reach from one building to another is equal to the absolute difference between the heights of buildings.

Note:

1. The heights of the buildings are positive.
2. Santa starts from the cell (0, 0) and he has to reach the building (N - 1, M - 1).
3. Santa cannot leave the grid at any point of time.

You are given a linked list of 'n' nodes and an integer 'k', where 'k' is less than or equal to 'n'.

Your task is to reverse the order of each group of 'k' consecutive nodes, if 'n' is not divisible by 'k', then the last group of nodes should remain unchanged.

For example, if the linked list is 1->2->3->4->5, and 'k' is 3, we have to reverse the first three elements, and leave the last two elements unchanged. Thus, the final linked list being 3->2->1->4->5.

Implement a function that performs this reversal, and returns the head of the modified linked list.

Example:

Input: 'list' = [1, 2, 3, 4], 'k' = 2

Output: 2 1 4 3

Explanation:
We have to reverse the given list 'k' at a time, which is 2 in this case. So we reverse the first 2 elements then the next 2 elements, giving us 2->1->4->3.

Note:

All the node values will be distinct.