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Given a linked list of size N. The task is to reverse every k nodes (where k is an input to the function) in the linked list. If the number of nodes is not a multiple of k then left-out nodes, in the end, should be considered as a group and must be reversed (See Example 2 for clarification).
Example 1:
POTD
POTD
Input:
LinkedList: 1->2->2->4->5->6->7->8
K = 4
Output: 4 2 2 1 8 7 6 5
Explanation:
The first 4 elements 1,2,2,4 are reversed first
and then the next 4 elements 5,6,7,8. Hence, the
resultant linked list is 4->2->2->1->8->7->6->5.
Example 2:
Input:
LinkedList: 1->2->3->4->5
K = 3
Output: 3 2 1 5 4
Explanation:
The first 3 elements are 1,2,3 are reversed
first and then elements 4,5 are reversed.Hence,
the resultant linked list is 3->2->1->5->4.
Your Task:
You don't need to read input or print anything. Your task is to complete the function reverse() which should reverse the linked list in group of size k and return the head of the modified linked list.
Expected Time Complexity : O(N)
Expected Auxilliary Space : O(1)
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