🧠 Before you code — what pattern fits?
Given the head of a singly linked list, group all the nodes at odd positions together followed by the nodes at even positions (1-indexed), keeping relative order within each group. Solve in O(1) space and O(n) time.
[1,2,3,4,5] → [1,3,5,2,4]
[2,1,3,5,6,4,7] → [2,3,6,7,1,5,4]
🎬 Video explanation · Nick White
Your solution runs against 3 unit tests, including edge and large-value cases.
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