Comment

MizardX

I tried optimizing the top competitors:

* f8 5.239
* f8b 4.415 <--
* f8c 4.971
* f11 5.692
* f11b 4.882
* f11c 4.713 <--
* f12 5.76
* f12b 4.911 <--

f12 is Mike Watkins' function.

f8b, f11b, f12b is unchanged except for storing a reference to seen.add/uniq.remove

f8c also tried to store a reference to seen.__contains__, which back-fired.

In f11c I tried to change if-continue-statements to if-not-statements, as Anonymous sugested.

Optimizing attribute lookup can give 15% speedup.
Removing continue statements can give another 5%.

Changing the in-operator to a call to __contains__ removes 10%.