Maximum Product Subarray

Question

## Problem

Find the contiguous subarray with the largest product.

## Example
```
[2,3,-2,4] -> 6
```

## Constraints
- 1 ≤ n ≤ 2 × 10^4

## Approach
Track running max and min (sign flips on negatives). O(n). Reported Salesforce OA question.