Let's make a deal!

[Sava]

Can I claim the person I stole the goats from is my wife?

filing a false police report is a sersiou crime

[loinburger]

This is trivially solvable through brute force, although I am sure there are more elegant solutions. It just isn't worthwhile to try to find them.

Am currently writing a short solution in python.

Enumerate the primes with the sieve of eratosthenes, stick them in a hash table, and test their rotations to see if they're in the hash table. And then eat a goat.

[Hauldren Collider]

Enumerate the primes with the sieve of eratosthenes, stick them in a hash table, and test their rotations to see if they're in the hash table. And then eat a goat.

LOL spoilers.

Damn, now I'm too lazy to finish my solution. I actually didn't know about the sieve of eratosthenes, so I was just doing modulo every number less than x to check primality. Yours is a very good way of doing it though.

I'll try doing it this way now. Will post results when finished.

[loinburger]

The sieve of eratosthenes is a good thing to know because for some reason job interviewers absolutely love to ask prime number enumeration questions.

[regexcellent]

Just like you should always be able to quickly explain quicksort. I can explain how quicksort works very succinctly and answer questions about it but if you actually asked me to write an implementation I'd probably just **** it up because the devil is very much in the details.

[Hauldren Collider]

OK, that took longer than it should have because I took a break to eat, but here's my solution:

  1 #simple circular prime solver
  2 def eratosthenes(max):
  3     nums = []
  4     primes = []
  5     for n in range(0, max):
  6         nums.append([n, 0])
  7     #edge cases
  8     nums[0][1] = -1
  9     nums[1][1] = -1
 10     #the sieve
 11     for n in range(2, max):
 12         if nums[n][1]: #status has been assigned
 13             continue
 14         for m in range(n, max, n):
 15             nums[m][1] = -1
 16         nums[n][1] = 1
 17         primes.append(n)
 18     return (nums, primes)
 19
 20 def circulate(x, nums):
 21     #make a list of the digits
 22     y = list(str(x))
 23     for n in range(0, len(y)-1):
 24         #rotate digits
 25         y.insert(0,y.pop())
 26         #convert back to int
 27         z = int("".join(y))
 28         if(nums[z][1] != 1):
 29             return False
 30     return True
 31
 32 (nums, primes) = eratosthenes(1000000)
 33 t=0
 34 a=[]
 35 for p in primes:
 36     if circulate(p, nums):
 37         a.append(p)
 38         t+=1
 39 print "Number of circular primes: " + str(t)
 40 print "Primes: " + str(a)
 41

And the result:

Number of circular primes: 55
Primes: [2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, 97, 113, 131, 197, 199, 311, 337, 373, 719, 733, 919, 971, 991, 1193, 1931, 3119, 3779, 7793, 7937, 9311, 9377, 11939, 19391, 19937, 37199, 39119, 71993, 91193, 93719, 93911, 99371, 193939, 199933, 319993, 331999, 391939, 393919, 919393, 933199, 939193, 939391, 993319, 999331]

Did I get it right, loinburger?

[loinburger]

Looks reasonable to me. My usual practice with Project Euler puzzles is to say "I probably could(n't) solve that" and to leave it at that.

[loinburger]

I think that over 90% of the real-life "puzzles" I've seen involve either deadlocks or race conditions or some combination of the two, and those are only really an issue if I can't switch to using optimistic concurrency for some reason (usually because my boss nixes the change because (s)he doesn't understand optimistic concurrency).

[regexcellent]

I think that over 90% of the real-life "puzzles" I've seen involve either deadlocks or race conditions or some combination of the two

Why everyone should take Operating Systems or some systems programming course

[snoopy369]

Why everyone should take Operating Systems or some systems programming course

I'm going to interpret "everyone" as meaning "everyone", and agree, even though you probably mean "everyone in compsci".

[loinburger]

I'd rather that compsci students were taught how to program using lock-free concurrency - the code scales better and is ten times easier to maintain.

And I'd rather that everybody not have to take an operating systems course - it's already a pain in the ass fixing my relatives' computers without their knowing how to use the fiddly bits in Windows.

[The Mad Monk]

The sieve of eratosthenes is a good thing to know because for some reason job interviewers absolutely love to ask prime number enumeration questions.

Thank you. That was a pleasant accumulation of knowledge.

[Hauldren Collider]

OS doesn't teach you about the fiddly bits in Windows. It teaches systems programming.

xpost

[Dinner]

What sort of microbrew would Dinner recommend to accompany goat meat?

Now that is a worthy question. I shall have to ruminate on it a while. Get it? Ruminate?
[/pun]

[Dinner]

No. Dinner threadjacked it into a goateating thread. Dinner likes food threads.

You should move away from the grazing goats, very dangerous in case of a marine invasion.

Oh, and technically Loinburger brought up eating goats before I did.