Search found 179 matches

by Sandor
Sun Jan 09, 2011 5:41 pm UTC
Forum: Logic Puzzles
Topic: Yet Another Cipher.
Replies: 8
Views: 3092

Re: Yet Another Cipher.

nicely done! Thanks! Curiously, if you convert the "hello world" example to base 8, you get 4511163727275460662. If you then map 57 to "a", 60 to "b", 61 to "c", etc. you get this: 04 51 11 63 72 72 75 46 06 62 e l l o d Which is tantilizingly close, and thre...
by Sandor
Sun Jan 09, 2011 8:37 am UTC
Forum: Mathematics
Topic: ln(x) or log(x)?
Replies: 63
Views: 9215

Re: ln(x) or log(x)?

I haven't used use logs much since school (so my opinion doesn't count for much), but I would go with log(x) for base 10 and ln(x) for e as well. I had always assumed that "ln" was derived from "log natural", or something similar. That's how I remember which is which. A search fo...
by Sandor
Sat Jan 08, 2011 3:38 pm UTC
Forum: Logic Puzzles
Topic: Yet Another Cipher.
Replies: 8
Views: 3092

Re: Yet Another Cipher.

Solved it. The plain text is from Moby Dick. Clue: Most definitely base related Solution: After some searching for a decent online base conversion utility, I found http://markknowsnothing.com/cgi-bin/baseconv.php which uses digits 0-9,A-Z,a-z, and says: 83641218461229490 converted from base 10 to ba...
by Sandor
Thu Jan 06, 2011 2:20 pm UTC
Forum: Science
Topic: Aluminum foil in a microwave - when should you be worried?
Replies: 24
Views: 13971

Re: Aluminum foil in a microwave - when should you be worrie

The kebabs round here come in wrapped in aluminium, which are then put in a special paper bag. The one time I tried to put one in the microwave, it produced a fairly spectacular light show and set fire to the paper bag. And the result tasted metalic. I'm not doing that again.
by Sandor
Thu Jan 06, 2011 1:49 pm UTC
Forum: Logic Puzzles
Topic: Secret Santa
Replies: 45
Views: 17772

Re: Secret Santa

Read what I wrote again. In order to satisfy the requirements of the problem stated at the start of this thread, we must force the probability of being in a 2-cycle to be exactly 1/(N-1) at the outset. I have read the requirements again, and am embarrassed to say I've been trying to solve the wrong...
by Sandor
Tue Jan 04, 2011 1:19 pm UTC
Forum: Logic Puzzles
Topic: Secret Santa
Replies: 45
Views: 17772

Re: Secret Santa

For a particular N, look at the different shapes of graphs of a derangement. For example, with N=8 we have a single 8-cycle, a 6-cycle and a 2-cycle, a 5-cycle and a 3-cycle, two 4-cycles, a 4-cycle and two 2-cycles, two 3-cycles and a 2-cycle, and four 2-cycles, for a total of seven different grap...
by Sandor
Wed Dec 29, 2010 4:06 pm UTC
Forum: Science
Topic: Can someone explain how Megajoules and railguns?
Replies: 24
Views: 3327

Re: Can someone explain how Megajoules and railguns?

Is this the energy consumed by the railgun, or the kinetic energy of the projectile? Kinetic energy = mv 2 /2 Let's say you're firing a 10 kilogram projectile from a railgun. 33*10 6 J = 10/2 kg * (v 2 ) v 2 = 6.6 * 10^6 m 2 /s 2 v = 2570 m/s = 9250 km/h Pretty much spot on. Jane's says it was a 10...
by Sandor
Tue Dec 21, 2010 12:53 pm UTC
Forum: Logic Puzzles
Topic: Here is a cipher to solve...
Replies: 2
Views: 1260

Re: Here is a cipher to solve...

Clue This is fairly simple, and jbwraith is on the right track. The game pre-dates the PS2, but you don't need to know the game to solve the cipher. Solution It uses 5 different Caeser ciphers, with shifts of the triangular numbers 0, 1, 3, 6 & 10. The reverse ciphers for decoding are: ABCDE...
by Sandor
Tue Dec 21, 2010 11:00 am UTC
Forum: Logic Puzzles
Topic: Word Pyramid
Replies: 19
Views: 5123

Re: Word Pyramid

Rule: Each answer can be obtained by rearranging the letters in the previous answer, with the addition of one more letter: PUZZLE 1: o no now down drown wonder one word Separating letters to make a space counts as part of the rearrangement. PUZZLE 2: i in tin mint twins Rotating "m" to ge...
by Sandor
Mon Dec 20, 2010 4:57 pm UTC
Forum: Logic Puzzles
Topic: License plate numbering scheme.
Replies: 8
Views: 2828

Re: License plate numbering scheme.

(2) Can complete sets of allowed license plate numbers (sets to which no license plate numbers may be added without breaking the rule) be of different cardinality? This is a yes/no question. My trial by computer says the answer is... Yes. A much simplified example is 3 digit binary plates. I think ...
by Sandor
Mon Dec 20, 2010 2:46 pm UTC
Forum: Logic Puzzles
Topic: Secret Santa
Replies: 45
Views: 17772

Re: Secret Santa

Person Q makes a derangement g of the numbers from 1 to N with zero 2-cycles. For example, a single N-cycle will work. The same person also makes a derangement h of the numbers from 1 to N with exactly one 2-cycle. For example, a single 2-cycle and a single (N-2)-cycle. If I have understood what yo...
by Sandor
Fri Dec 17, 2010 5:47 pm UTC
Forum: Logic Puzzles
Topic: Secret Santa
Replies: 45
Views: 17772

Re: Secret Santa

Sorry for the double post, but these are some new thoughts... For 7 people the possible graphs are: ⋅ Two 2-loops and a 3-loop: 210 derangements ⋅ A 2-loop and a 5-loop: 504 derangements ⋅ A 3-loop and a 4-loop: 420 derangements ⋅ A 7-loop: 720 derangements To...
by Sandor
Fri Dec 17, 2010 12:47 pm UTC
Forum: Logic Puzzles
Topic: Secret Santa
Replies: 45
Views: 17772

Re: Secret Santa

I have a thought, but it’s 2:30am now so there’s a good chance I forgot something. Nonetheless, here’s what I’ve come up with as a way for a group of N people to make a secret-Santa-style derangement of themselves with no outside help and with no one learning anything other than the identity of the...
by Sandor
Wed Dec 15, 2010 6:25 pm UTC
Forum: Logic Puzzles
Topic: Secret Santa
Replies: 45
Views: 17772

Re: Secret Santa

This took over my brain for way too long. You're not joking! Anyway, I think I have it. Edit: No I don't have it - this doesn't work :( 1. Secret Santa with bounded number of operations and correct probabilities. Put everyone's name into a hat. Each person pulls a name out in turn. This is the ...
by Sandor
Fri Nov 12, 2010 6:32 pm UTC
Forum: Coding
Topic: minesweeper
Replies: 32
Views: 2952

Re: minesweeper

EDIT: i fixed it and it now works: /*...*/ if (mineMap[i + 1][j + 1] != '*' && !(i + 1 > 3) && !(j + 1 > 3)) (mineMap[i + 1][j + 1] += 1); if (mineMap[i - 1][j - 1] != '*' && !(i - 1 < 0) && !(j - 1 < 0)) (mineMap[i - 1][j - 1] += 1); /*...*/ I don't think anyone has...
by Sandor
Fri Jul 02, 2010 3:17 pm UTC
Forum: Coding
Topic: Computed includes in C
Replies: 26
Views: 3098

Re: Computed includes in C

To answer the original question, or at least the "how to fix it?" bit, the C99 standard says this about macro replacements: 6.10.3.4 3 The resulting completely macro-replaced preprocessing token sequence is not processed as a preprocessing directive even if it resembles one, [...] So even ...
by Sandor
Sat Jun 19, 2010 12:03 am UTC
Forum: Science
Topic: Weird Effect on Google Maps
Replies: 40
Views: 5607

Re: Weird Effect on Google Maps

The image looks a little too high a resolution for commercial satellite imagery to me, although maybe not for military satellites. The copyright information in the image mentions GeoEye ( http://www.geoeye.com/ ) who do do 0.5 meter resolution satellite imagery, but they also do aerial. The website ...
by Sandor
Fri Jun 11, 2010 3:51 pm UTC
Forum: Coding
Topic: Shared library linking - undefined symbol
Replies: 10
Views: 2566

Re: Shared library linking - undefined symbol

libwiiuse.so defines the symbol wiiuse_find, but when I then go to load my library (in Lua, which uses dlopen): lua: error loading module 'wiimote' from file '/home/hyperhacker/dev/lua/libs/wiimote.so': /home/hyperhacker/dev/lua/libs/wiimote.so: undefined symbol: wiiuse_find Seems at runtime, it ca...
by Sandor
Sat Feb 13, 2010 8:35 am UTC
Forum: Science
Topic: Static Equilibrium Question : F.B.D. help
Replies: 9
Views: 1904

Re: Static Equilibrium Question : F.B.D. help

Treat the boy, the beam, the pulley and the angled part of the rope as all one system, and just look at the external forces acting on it:

Statics Equilibrium Problem 2.png
External Forces


That should make it simple.

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