Pack Consecutive Duplicates Into Sublists

Question

## Problem

Group consecutive equal elements of a list into sublists (run-length grouping).

## Example
```
[a,a,b,c,c,c] -> [[a,a],[b],[c,c,c]]
```

## Constraints
- 0 ≤ n ≤ 10^4

## Approach
Single pass comparing to the previous element. Reported Cisco question.