Reorder Existing Nodes from Alternating List Ends
Company: Google
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Other
### Problem
Reorder the existing nodes of a singly linked list by alternating from its beginning and end. If the original node identities are `L0,L1,...,Lk`, the result is `L0,Lk,L1,L(k-1),...`. Do not change any node's stored value.
```cpp
void reorderList(ListNode* head);
```
Keep the original `ListNode` objects and mutate their next links; the function returns nothing. Display brackets show node values along the chain.
### Examples
```text
Input: head = [2,5,8,11,14]
Chain after call: [2,14,5,11,8]
```
```text
Input: head = [3,6,9,12]
Chain after call: [3,12,6,9]
```
### Constraints
- There are between 1 and 50000 nodes.
- Values are between 1 and 1000, inclusive.
Overview: Reorder existing list nodes in first-last alternating order by splitting, reversing and weaving next links.