The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime.
There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97.
Given a number x, write a MATLAB script that will tell you the number of circular primes less than or equal to x as well as a sorted list of what the circular prime numbers are.
Solution Stats
Problem Comments
-
5 Comments
Show
2 older comments
Ryan
on 5 Dec 2012
Very nice problem!
Christopher
on 5 Dec 2012
How do you return two separable outputs via a single vector?
James
on 6 Dec 2012
Christopher, I should have been more clear in the problem description.
There are two outputs to the function. The first output (how_many) is a scalar, and is the number of circular primes.
The second output (what_numbers) is the vector containing the values of the circular primes.
Does this help?
Christopher
on 18 Dec 2012
197 is not circular prime, because neither 791 nor 917 are themselves prime. Only test case 2 is correct.
James
on 19 Dec 2012
Christopher, if our number is represented as ABC, then a cicrular prime is a number where ABC, BCA, and CAB are all prime. You are either shifting the numbers in the opposite direction or scrambling them. Not every permutation of the numbers has to be a prime number, although that in itself would be an interesting Cody problem. :-)
Solution Comments
-
1 Comment
Jean-Marie Sainthillier
on 19 Mar 2013
Size world record ?
-
1 Comment
Aurelien Queffurust
on 12 Dec 2012
circul -ez y a rien à voir :)
Problem Recent Solvers81
Suggested Problems
-
Replace NaNs with the number that appears to its left in the row.
1735 Solvers
-
Calculate the Levenshtein distance between two strings
312 Solvers
-
Flip the main diagonal of a matrix
434 Solvers
-
Set the array elements whose value is 13 to 0
759 Solvers
-
107 Solvers
More from this Author80
Problem Tags
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
Select web siteYou can also select a web site from the following list:
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)