Recognise the Multifactorial
code-golfmatharithmeticnumber-theorynumber (Suggestions welcome!)
We all know the factorial n! = n(n-1)(n-2)...2*1. Many of you will also have heard of the double factorial n!! which is not (n!)! but n(n-2)(n-4)... instead. Likewise, we can define other multifactori...
of course it would nicer to give code that make the test cases but I know peopel complain about any code
saying something like "I knwo I have been coding for 20 years and love to answer cryptic and complicated coding questions on the web in 10^45 different weird and wonderful languages.. But HOW AM I EXPECTED TO INSTALL PYTHON??!!"
I agree that the challenge's scoring wasn't very good, but including one of the test cases in the code is definitely hardcoding in my opinion. But we've discussed this in the comments. Let's just agree that you abused a bad part of the spec, which certainly a loophole, standard or not.
Anyway, I...
@user2179021 the code should make that list. but unless you provide one individual output, the benchmark set will vary every time you run it. (or provide the PRNG seed that is used for the set that scores the entries in the end.)
I suppose you should just write some code that generates a random syntax tree recursively (to some depth, which you should probably disclose), and then fill it with random numbers (up to some maximum, which you should probably disclose). plus maybe some sanity check that the numbers don't go through the roof.
@NewSandboxedPosts if you really want the focus to be on the grouping rather than factoring, I think you might want to grant people a single-character factorisation function for free. Otherwise J would get even more undue benefit than usual, I think
still, it would require people to implement a reasonably fast factorisation so I can actually test that they complete for 2^64 in a reasonably amount of time
it's a triple loop... the outer of the factorial order, the next over the offset, and the inner one just adds numbers until you exceed the target
this might be more boring that I thought
the only way around that I can see is to provide the prime factorisation instead of the number, and to make the numbers bigger than 2^64, disallowing use of numbers that large in the code
in fact, if you pick the operators randomly, you'll get varying depth automatically, because some operators are binary and some are unary
so you can really just build the tree completely randomly by choosing one of the primitives at random, maybe ignoring binary operators after depth 4 or so.
when you get to a number, pick a random number in some range (possibly skewed to lower numbers)
@PhiNotPi No the problem is that I don't have Wingdings.
☺
"In this first problem, there is a car driving along a cliff, and the car just jumps off. This person has decided to end it all. Now, we want to know at what time the car hits the ground. This is the beauty of physics, because if this were a psychology class we'd want to know why the person was jumping, but we are simply concerned with how long it takes." ~ Dr. Shankar, Physics I lecture at Yale
@user2179021 no, but would make the generating code easier. because if it's not integer divison, I'll have to throw away a lot of candidates including division because they won't result in integer results.
I have a problem with codegolf.stackexchange.com/q/41648/18487. Even if I don't hard code the answer, I could have it start searching at a point very close to an large fragile prime. What's stopping me from doing that?
Intro
Consider the process of taking some positive integer n in some base b and replacing each digit with its representation in the base of the digit to the right.
If the digit to the right is a 0, use base b.
If the digit to the right is a 1, use unary with 0's as tally marks.
If there is no ...
Ok so seriously, someone help me find all of the already asked performance related meta questions that sounds like "Do I need to specify the hardware it will be run on?"
I'd go with option F. Here are the rules for option F:
Requirements:
Askers MUST provide one or more explicit input test cases to be optimized.
For example, if the input to the program is x, the question could be specified to optimize for inputs x=5, x=50, and x=500.
Each code must compute ...
The current site statistics can be found here:
http://area51.stackexchange.com/proposals/45128/puzzling
[UPDATE:
PREVIOUSLY WE HAD 4/5 EXCELLENT STATS ON AREA 51 - NOW WE HAVE 5/5 EXCELLENT STATS, WE HAVE ACHIEVED A PEREFCT SCORE CARD. WHATEVER IT IS WE ARE DOING HERE WE MUST KEEP ON DOING - ...
No, the problem is that some users don't see it that way (and some do). They're just trying to figure out what makes a "good" question due to the recent flood of riddles and the like.
basically, a .SE website works if the sort of people who are interested in that sort of topic a) are the sort of people who like to look things up on the internet and b) are the sort of people who don't mind openly sharing their ideas
cstheory doesn't work as people are scared about saying anything new which they could otherwise have published
cooking.SE doesn't work as cooks have other places to find cooking advice
Speaking of which, I need to figure out the best way to make a pumpkin cheesecake this year. I've done it layered in the past (pumpkin on bottom, cheesecake on top), but I'd like to see if I could swirl them together a bit before baking to mix them in. I'm not sure if it will end up baking right, though, and don't want to "waste" one to find out.
So I have three rules written down now: 1. A fragile prime must end with 1 or 9. 2. If it ends with 9, it must begin with 4, 6, or 9. 3. If it ends with 1, it must begin with 8.
I'm no closer to understanding an algorithm for generating them. I can only generate primes and then check them after the fact.
But those three rules speed up the check by a few orders of magnitude.
I just forwarded this challenge to my former Mathematics professor who taught "Applications of Mathematics in Programming" in Python. He's a younger guy (with a PhD) who also happens to play Magic, so I'm sure he'll get a kick out of this.
I told him that the one thing I missed in his class was coming up with a new algorithm. We only studied problems that had been beaten to death.
Of course, there's a good reason for that. Most of the unsolved problems are totally useless, or just twisted combinations of problems that have been solved.
Consider the function Remove(n, startIndex, count) that removes count digits from the number n starting from the digit at position startIndex. Examples:
Remove(1234, 1, 1) = 234
Remove(123456, 2, 3) = 156
Remove(1507, 1, 2) = 07 = 7
Remove(1234, 1, 4) = 0
We will call the prime number X fragil...
I can generate a really large prime, but that's about it: 9441320041016089207490203515397709842252566482250916237077817028753504634211893531288337046081449069
About the fragile primes question, if it interests anyone the established terminology for a string with a substring removed from it seems to be 'outfix'
When searching around a bit I found cs.yonsei.ac.kr/~emmous/papers/ictac05.pdf which is about outfix-free codes (akin to prefix-free codes, i.e. no string in the language is an outfix of another string in the language)
At my school, the AP Economics class is doing a stock market competition. There is a website that allows people to trade fake money and stocks using the actual market data.
Here's the thing: I'm not in AP Econ.
So I created an account, found the group, and then guessed the password to be a part of it.
Intro
Consider the process of taking some positive integer n in some base b and replacing each digit with its representation in the base of the digit to the right.
If the digit to the right is a 0, use base b.
If the digit to the right is a 1, use unary with 0's as tally marks.
If there is no ...
I'd go with option F. Here are the rules for option F:
Requirements:
Askers MUST provide one or more explicit input test cases to be optimized.
For example, if the input to the program is x, the question could be specified to optimize for inputs x=5, x=50, and x=500.
Each code must compute ...
The current site statistics can be found here:
http://area51.stackexchange.com/proposals/45128/puzzling
[UPDATE:
PREVIOUSLY WE HAD 4/5 EXCELLENT STATS ON AREA 51 - NOW WE HAVE 5/5 EXCELLENT STATS, WE HAVE ACHIEVED A PEREFCT SCORE CARD. WHATEVER IT IS WE ARE DOING HERE WE MUST KEEP ON DOING - ...
Consider the function Remove(n, startIndex, count) that removes count digits from the number n starting from the digit at position startIndex. Examples:
Remove(1234, 1, 1) = 234
Remove(123456, 2, 3) = 156
Remove(1507, 1, 2) = 07 = 7
Remove(1234, 1, 4) = 0
We will call the prime number X fragil...
