As a first step towards classifying the solutions, I have timed them, just as I did for Rick's Troppo Sort game.
The winner of this month's Tortoise-crawlin' Hall of Shame award is Amir Karger. It seems that Perl's Recursive Regex is rather slow. I have tried to classify some of the solutions below. If I have made any mistakes, please let me know. And please feel free to classify your own solutions (that will definitely be more accurate than my feeble guesses;-). Score Seconds Method ----- ------- ------ 1. Ala Qumsieh 210.77 0.95 Stack (operator) 2. Mtv Europe 125.38 1.02 Stack (operator) 3. Alma Media Golf Team 119.62 1.05 Stack (all) 4. GONZO 322.75 1.06 Stack (operator) 5. Constantin M 292.43 1.38 6. Michiel van Leeuwen 144.65 1.44 7. Andrew Savige 133.69 1.46 Stack (operator) 8. Qingning Huo 116.27 1.48 9. Andre Savigne 1666.36 1.48 Stack (operator) 10. Peter Haworth 316.87 1.84 11. Kuang-che Wu 143.72 1.98 12. Jeff Moore 116.48 2.15 Overload 13. Jed Davis 177.58 2.34 Overload 14. Markus Laire 127.65 2.60 15. Adam Antonik 120.8 2.65 Overload 16. TheodoreYoung 131.82 2.76 Overload 17. Mykola Zubach 121.6 2.79 18. Jasvir Nagra 132.8 2.85 Overload 19. Ton Hospel 103.33 3.11 Parse (top down[2]) 20. Eugene van der Pijll 98.22 3.26 Mad Dutch[1] 21. nashdj 209.69 3.43 Recursive Regex 22. Stephen Turner 116.65 3.72 Overload 23. Mark Hillebrand 121.6 3.81 24. Chris Dolan 153.48 4.31 25. Jonathan Wang 176.64 4.92 26. Keith Calvert Ivey 133.62 5.05 27. Michael Thelen 112.63 5.96 Stack (operator) 28. me ELOISE 206.7 6.20 29. John Williams 142.58 6.47 30. Prakash Kailasa 162.7 6.77 31. Jasper McCrea 172.39 7.99 32. Alain "TopMach" Dupuis 118.57 12.45 33. Chia-chi Yeh 121.62 13.45 34. Greg Allen 206.56 14.24 Parse (hybrid) 35. Honza Pazdziora 267.25 15.27 36. pom 109.51 18.49 Mad Dutch[1] 37. tinzo (berlin.pm) 165.45 41.36 Stack (with a hint of Mad Dutch[1]) 38. Alexey Rudenko 109.51 48.34 Recursive Regex 39. Jukka Suomela 149.25 49.87 40. Rick Klement 102.3 69.65 41. Eike Grote 203.63 92.12 42. Amir Karger 140.46 110.90 Recursive Regex [1] finite state transducer (?) [2] aka recursive descent Why is Ala the fastest? Probably because of all that push'n'pop'n. Notice that Ala is the only golfer who used 'reverse'. Now, push/pop are pretty fast, faster than shift/unshift. However, the golfing price for all that push'n'pop'n is that butt-ugly 'reverse' adorning the end of Ala's solution. To avoid the reverse, you might create the operator stack with shift/unshift (as I tried in my first submission). To eliminate the unshift eyesore, I soon switched to a string-based stack manipulated by Regexes. To see push'n'pop'n done well, see Alma Media's 119.62 (where they push both numbers and operators onto the stack, I think). /-\ndrew