It also depends on the assumptions we make about the problem.

- Do we have to validate the URL strings in any way?

- What do we need to do with duplicate names?

- Are cases with small parameter names and/or small numbers of parameters common?

- How common are parameters with lengthy common prefixes?

- Is there a bound on the length of the longest common prefix of two different parameter names?

Tuning or special-casing with common cases in mind can often produce big wins.