Reverse Alternate K Nodes

Given a linked list A of length N and an integer B.

You need to reverse every alternate B nodes in the linked list A.

• 1 <= N <= 10⁵
• 1<= Value in Each Link List Node <= 10³
• 1 <= B <= N
• N is divisible by B

First argument is the head pointer of the linkedlist A.

Second argument is an integer B.

Return the head pointer of the final linkedlist as described.

Input 1:

 A = 3 -> 4 -> 7 -> 5 -> 6 -> 6 -> 15 -> 61 -> 16
 B = 3

Input 2:

 A = 1 -> 4 -> 6 -> 6 -> 4 -> 10
 B = 2

Output 1:

 7 -> 4 -> 3 -> 5 -> 6 -> 6 -> 16 -> 61 -> 15

Output 2:

 4 -> 1 -> 6 -> 6 -> 10 -> 4

Explanation 1:

 The linked list contains 9 nodes and we need to reverse alternate 3 nodes.
 First sublist of length 3  is 3 -> 4 -> 7 so on reversing it we get 7 -> 4 -> 3.
 Second sublist of length 3 is 5 -> 6 -> 6 we don't need to reverse it.
 Third sublist of length 3 is 15 -> 61 -> 16 so on reversing it we get 16 -> 61 -> 15.

Explanation 2:

 The linked list contains 6 nodes and we need to reverse alternate 2 nodes.
 First sublist of length 2 is 1 -> 4 so on reversing it we get 4 -> 1.
 Second sublist of length 2 is 6 -> 6 we don't need to reverse it.
 Third sublist of length 2 is 4 -> 10 so on reversing it we get 10 -> 4.