..:: wu : riddles ::..
[ hardcore tech-interview style riddles and mathematical puzzles. daily high-quality forum discussions. Milli0ns served! ]
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..:: faq ::..
  1. Where are the answers?
    • Excellent answers for 99% of the problems are available in the riddle forum. You can use the search function to help locate the puzzle's thread. Although we forum administrators try to maintain only one thread per puzzle, some puzzles have multiple threads.

  2. Why don't you just display the answers directly on the cover site? Searching for solutions in the forum can be inconvenient.
    • One reason I do not show answers directly is because this would spoil the problem-solving experience for many visitors. If the answers are too accessible, I'm afraid visitors would be too easily tempted to give up. My hope is that visitors will use this opportunity to exercise their minds, and really try to solve the problems on their own first before seeking help. Another reason is that by reading an argumentative dialogue that eventually converges to the solution, you will have a better glimpse of the underlying thought processes that took place, as opposed to simply reading a straight-forward description of the solution. There are often many ways of getting to an answer, and having an open forum increases the chances of covering all the different ways. The process of solving a puzzle is more relevant than the solution itself. See this thread for further discussion on why answers aren't direclty shown.

  3. Where should I start?

  4. How long have you been collecting riddles?
    • During my junior year at UC Berkeley, I started maintaining a mental cache of riddles that I liked. Then in the spring, I began writing them down and aggressively searching for more. I am avid lover of all things clever and creative.

  5. How can I contribute a riddle?
    • Visitors can post new riddles to the forum, from which I may eventually export them to the cover site. Or, they can e-mail me. (Remove the "NO_SPAM_" prefix when sending.)

  6. How can I find out what riddles have been added recently?
    • The best way to get the latest scoop on riddles is to join the forum. New puzzles are posted there daily, and you can check the 10 most recent posts. If you're not down with the forum for whatever reason, you can check out the front page of this cover site, where I list the most recent additions. However, the cover site is updated only once in a while, when I have a large batch of new ones to add. It is also worth noting that the drop down menus of riddles are listed in chronological order, from oldest at the top to newest at the bottom.

  7. Where is this slashdot article about your site?

  8. Where else has the site been featured?
    • Some places the site has been mentioned include the puzzle corners of MENSA newsletters, and in a mathematical journal publication regarding the 100 Prisoners and a Light Bulb problem. The site is recommended in William Poundstone's book of Microsoft interview questions, How to Move Mount Fuji. Also it has been used as a teaching aid for ESL students. Many problems from the site have since propagated across the web.

  9. What kind of traffic do you get? / What was the traffic like during slashdot?
    • I haven't processed all the apache logfiles yet, so I can't say exactly. The site was posted on slashdot at 11:47 PM on Tuesday, July 23. Immediately afterwards, I received about 100,000 hits in the space of 20 hours. OCF.Berkeley.EDU temporarily shut down, but then they added more swap space. This shut down may actually have been due to my improper chmod settings on files related to the forum, which then resulted in file-locking issues. Perhaps the traffic would have been multiplied many times over had the OCF server not been so sluggish that day due to my mistake. Similar traffic continued for the rest of the week and gradually tapered off. Currently I might be getting a couple thousand hits a day; I'll check these figures later. (update 1/28/2003 12:56AM: pretty sure traffic is no longer nearly as heavy, but I don't since I still haven't checked ... hehe so lazy)

      The above graph shows a peak of "inbound" bandwidth at the time of slashdot's posting. This is actually inbound to the router interface on the local subnet, which is really outbound in the direction from the local subnet to the rest of campus and the rest of the world. If the slashdot effect were real, we would expect to see lots of "outbound" packets (from the router interface to the local subnet) in addition to the inbound bandwidth peak. This cannot really be seen on the bandwidth graph - the "outbound" bandwidth doesn't peak much. However, HTTP GET requests take up so little bandwidth that it might not even show up on this graph. Thus, in addition to bandwidth, we must also look at packet rates, which are on a separate graph:

      Here we see both an inbound and outbound packet peak. So, it looks like slashdot did have an effect. Also note that the area of the bandwidth and packet curves are larger than they normally are for the remainder of the week. Special thanks to the friendly Michael Sinatra for explaining how to interpret these graphs.

page last modified Thursday, 17-Feb-2005 21:01:40 PST

Thanks to Contributors David Lau, Siddhartha Doshi, Jiong Shen, Carl Wang, Phoebus Chen, Alan Liu, Hansen Bow, Ernest Zhu, Elaine Lo, Yosen Lin, Don Barkauskas, Katherine Chan, Jasvir Nagra, Tau Beta Pi (TBP), Eta Kappa Nu (HKN), Danny Dulai, His Grace The Duke Of Ankh-Morpork Commander Sir Samuel Vimes, Michael Snyder, Dipan K. Ghosh, Eric Cole, Louis Wainwright, Ben Bardill, Patrick Dreker, Autumn Looijen, Stephen Champailler, Christopher Kings-Lynne, Bart Samwel, Kannan Ramchandran, Nick Yee, Steve Plimpton, Levsen Hendrik, Remco Hartog, [I.M._Smarter_Enyu], Philip Mock, Michael Chang, Jon Meilstrup, Ryan Russell, Matt Young, Jonathan Haas, Geoff Canyon, Peter Surda, Cory Ondrejka, Satish Rao, [gcooper], Ted Powell, Brave Sir Robin, Eric Cole, J. A. H. Hunter, Sean R. Owen, Andrew Glenn, Bruce Preston, Peter Ratiu, Michael Mendelsohn, Rob Mahurin, James Fingas, Bryan Organ, Jeroen Rutten, Stephen Montgomery-Smith, Marko Lukat, Eric Yeh, Nick Hobson, Mike Lawther, [anshil], Richard Feynman, Douglas Hofstaeder, Dacher Keltner, David Mace, [SAS], Matthew Schultheis, John Leen, Andrew Ooi, Folkert Hindriks, Steve Ragle, Daniel Filner, Karl Barrus, Misha Kruk, Keith Lloyd, Dave Minott, Jette Randlov, Eric Winger, Nathan Hellweg, Tom VanCourt, Chris Seaton, Mitchell Morris, Michael Styer, Zameer Andani, Jonathan Blow, Jeff Thompson, Jonathon Duerig, Dan Hanson, Gabriel Sechan, Tom Saxton, [HunterWare], [alsee], James Antill, Tom Barringer, Bart Massey, David Krikorian, Eric Sharkey, [tudorb], Kevin Day, Milan Ramaiya, Robert Merkel, James Jones, Haim Bitner, Adam Barth, Oscar Lazzarino, Damien Fisher, [DrkShadow], Erik Blankendaal, Eric Smith, James Demmel, Jonathan Shewchuk, Alex Harris, Michael Kelley, [Mr._Martingale], Kaisen Lin, Hakan Yilmaz, Freddy Mercury, Justin Rising, Marko Lukat, William Kahan, Jeremy Randolph, Michael Sinatra, David Messerschmitt, Patrick Masterson, Frederik Bonte, Randy Williams, Pietro K.C., Brett Danaher, Derek Abbott, Ralph Boleslavsky, Rui del-Negro, [college math journal], [amer. math monthly], Spyros Potamianos, Gary Hsieh, [rec.puzzles], Steven Rudich, Matt Lahut, Richard Reti, Paul Sinclair, Tim Mann, [ucb engineering news], Luke Percival, Anwis Das, Mike White, Louise Poon, Jeffrey Wilhelm, Anthony Cammon, [BNC], A.Frieze & D.Sleator, [SWF], Ted Stevens, Frank Wang, Danny P, Patrick Sesulka, [towr], Chi Sum Cheung, Ranjit Jhala, Jacob Scott, David McKay, Eamon Warnock (THUDandBLUNDER), Kozo Morimoto, Abhijit Joshi, Devesh Parekh, Amnon Melzer, Mary Lou, Leonid Brouhkis, Allistair Sinclair, Mark Newheiser, Joc Koelman, Paul Jung, Aryabhatta, Thomas Cover, Barukh, Nootch, Eigenray

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