Problem 2910. Mersenne Primes vs. All Primes

Created by goc3

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Solution Stats

991 Solutions
368 Solvers

Last Solution submitted on Mar 30, 2023

Last 200 Solutions

Problem Comments

1 Comment

1 Comment

Jean-Marie Sainthillier on 16 May 2019

Hello Grant,
I don't know if it's a lot of work but it could be a good idea to add a Prime Numbers group 2 with more difficult problems. I think about beautiful Ned's problems (primes ladders, Longest prime diagonal, Twins in a window ...).

Solution Comments

Solution 6817490

1 Comment

1 Comment

Jan-Andrea Bard on 3 Nov 2021

Nice one. I found a solution of size 127. And I have the impression it's already quite condensed. It's a mystery to me how one can write a solution of size 26. Can anybody give me a hint on how to do so?

Solution 4370990

2 Comments

2 Comments

Ozer Eroglu on 20 Dec 2020

test cases are wrong.
please be more serious to accept problems.
it doesn't suit mathworks:(

Dyuman Joshi on 21 May 2021

@Ozer Eroglu
Test cases have been verified and they are indeed correct. What makes you think so that they are wrong?

Solution 1931803

1 Comment

1 Comment

Mayank Bajpai on 5 Oct 2020

Does all the leading solutions with the size below 10, use this ? Nice idea, but this doesn't improve the problem solving skills.

Solution 571313

6 Comments

6 Comments

Show 3 older comments

Anupam Agarwal on 1 Feb 2015

My logic is right but test cases are very hude numbers.... failed to evaluate...

Guillaume on 2 Feb 2015

You need to learn to avoid loops. You can use isprime on an array. In any case, your logic is wrong. You never test that b is prime.

goc3 on 2 Feb 2015

As Guillaume pointed out, this solution doesn't test if the numbers in b are Mersenne primes, simply if they're less than 2^n-1, which is not the right criterion. Further, you concatenate the index of the loop (j, which goes from 1 to 1...), rather than a Mersenne prime to b.

Also, this problem is designed, as many of James's problems are, to fail by timeout unless vectorized solutions are used.

Anupam Agarwal on 3 Feb 2015

i have corrected the logic but plz can u tell me smthing about vectorized solutions...
u can also mail me on anupamagarw@gmail.com

Jan Orwat on 3 Feb 2015

http://nl.mathworks.com/help/matlab/matlab_prog/vectorization.html

Jan Orwat on 3 Feb 2015

some tips: http://nl.mathworks.com/help/matlab/matlab_prog/techniques-for-improving-performance.html

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