Reverse Nodes in k-Group

Given the head of a singly linked list, reverse the nodes of the list

k

at a time and return the modified list.

k

is a positive integer and is guaranteed to be less than or equal to the total number of nodes. If the number of nodes is not a multiple of

k

, the left-out nodes at the end should remain in their original order. You must perform the reversal in-place without modifying the values within the nodes; only the node pointers themselves may be changed. Example: Input: head = [1,2,3,4,5], k = 2 Output: [2,1,4,3,5] Constraints: The number of nodes in the list is

n

1 \le k \le n \le 5000

0 \le Node.val \le 1000

PythonLinked ListIterative Algorithm

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