**Reorder List** =============== **Problem Statement** ------------------- Given the head of a singly linked list, reorder it such that the nodes in the list are arranged in an alternating left-to-right and right-to-left manner, while keeping the original relative order of the nodes. **Rules and Constraints** ------------------------- - The linked list should be non-empty. - The linked list nodes are singly linked (i.e., each node contains a pointer to the next node, but not to the previous one). - The reordering should be done in-place, without creating any additional nodes or modifying the original linked list structure. **Input/Output** ---------------- The input to the problem is the head of a singly linked list, and the output is the modified linked list with the nodes reordered according to the problem statement. ### Example **Input:** {"head":[1,2,3,4]} **Output:** [1,4,2,3]