Reverse a Linked List / Detect Cycle

Question

## Problem

Reverse a singly linked list and detect whether it has a cycle.

## Example
```
1->2->3 => 3->2->1; cycle via Floyd
```

## Constraints
- 0 ≤ nodes ≤ 10^4

## Approach
Classic pointer manipulation; Akamai probes linked-list and memory questions.