Linked List

Structure Shift: Reversing Nodes in K-Groups

Feb 2026

11 min read

Reversing groups of K nodes is the ultimate test of linked list proficiency. It requires perfect synchronization between local reversal and global pointer stitching.

Implementation

java

class Solution {
    public ListNode reverseKGroup(ListNode head, int k) {
        ListNode temp = head;
        for (int i = 0; i < k; i++) {
            if (temp == null) return head;
            temp = temp.next;
        }

        ListNode curr = head, prev = null, next = null;
        for (int i = 0; i < k; i++) {
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }

        if (next != null) head.next = reverseKGroup(next, k);
        return prev;
    }
}