The Goldbach conjecture asserts that every even integer greater than 2 can be expressed as the sum of two primes.
Given the even integer n, return primes p1 and p2 that satisfy the condition n = p1 + p2. Note that the primes are not always unique. The test is not sensitive to order or uniqueness. You just need to meet the appropriate conditions.
Example:
Input n = 286
Output (any of the following is acceptable)
[ 3 283]
[283 3]
[ 5 281]
[107 179]
[137 149]
Solution Stats
Problem Comments
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13 Comments
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10 older comments
Mineralter
on 26 Jun 2013
for n =10,p1=[3 5 7],p2=[7 5 3],is the correct answer. but the judgement is not allowed.
Robert Johansson
on 10 Aug 2013
Nice one.
Alexander Razmyslov
on 5 Feb 2015
Thank you very much! Its a really nice one!
Jonathan Campelli
on 24 Feb 2015
Well made. I am still trimming down my code furiously. My favorite problem so far.
Matteo Tessarolo
on 6 May 2016
Currently the best one for me!
Ahmed Abdelbasit
on 12 Feb 2017
nice problem . I like problem related to prime numbers
Fabio Masino
on 24 Aug 2017
Very nice problem!
Vincent Kroeze
on 3 Jan 2018
this was a fun one
GEORGIOS BEKAS
on 26 Jan 2018
something I am doing worng.
please help.
p1=[]
p2=[]
for i = 1:5000
x1 = ceil(286*rand(1));
x2 = ceil(286*rand(1));
s = x1+x2;
a =isprime(x1);
b=isprime(x2);
if a==1 && b==1 && s ==n
p1=x1
p2=x2
end
end
[p1 p2]
Jiahang Li
on 1 Feb 2018
cool
Da Lu
on 7 Mar 2018
有中国的小伙伴吗？
Pablo López
on 8 Feb 2019
Really interesting the Goldbach conjecture!
Olivia Li
on 29 May 2019
有中国的小伙伴呀
Solution Comments
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1 Comment
Simon Thomas
on 17 Sep 2019 at 10:29
Happier now. Loop though nList handled in test suite. No loop in my function and returns the 2 primes closest together
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1 Comment
Simon Thomas
on 17 Sep 2019 at 10:11
given that the looping through nList is handled in the test suite, I don't need to.
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1 Comment
Sanzhar Askaruly
on 19 Jun 2019
returning single value of prime pair instead of vector will help
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1 Comment
Paul Smits
on 13 Apr 2019
with functions like nchoosek and primes, it is quite easy
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1 Comment
Xinyue Zhou
on 15 Apr 2018
tai tama nan le.:)
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2 Comments
Jens Christiansen
on 11 Sep 2017
Forgetting 1 isn't prime doesn't help
David Verrelli
on 24 Sep 2017
See https://en.wikipedia.org/wiki/Prime_number#Primality_of_one
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2 Comments
ahmed nasr
on 14 Jun 2017
my solution is correct,, what is the problem
Pavol
on 16 Jun 2017
Problem is with the test suite it expects just 2 numbers and you generated vector of all possible solutions, if you return after finding the first pair it will work.
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1 Comment
Joe Smith
on 28 May 2016
Lists all of them.
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1 Comment
Fatpuss
on 13 Dec 2015
High score but simple and two lines.
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2 Comments
Lane Foulks
on 19 Nov 2015
Can't use combnk()? Getting an error for using?
Lane Foulks
on 19 Nov 2015
Oh, I can use nchoosek() instead...
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1 Comment
Daniel Warren
on 28 Jul 2015
Bizarrely I couldn't submit this solution when b, b1 and b2 were labelled p, p1 and p2 due to 'inappopriate content'. I'd be interested to know what looked so inappropriate...
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1 Comment
Nafus
on 7 Jul 2015
Why is this not working?
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1 Comment
Ze Zhang
on 17 Mar 2015
n - (1:n) can be written as (n-1):-1:0
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1 Comment
Diego
on 30 Dec 2014
This one passed tests, but solves another problem: p1 is odd and p2 is prime. It fails to find 2+2=4 and finds incorrectly 9+89=98.
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1 Comment
Kai
on 16 Sep 2014
This is the best I can do...
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1 Comment
Kirk
on 23 Jul 2014
Although the naming of primes is a poor choice,
primes = primes(nums);
can replace:
nums=2:n;
primes=nums(isprime(nums));
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1 Comment
Peng Liu
on 25 Mar 2015
Although it passes the test suite, this solution is incorrect for n = 4, 6. The main reason for this error is that the nested loop for j is incorrect. It should be for j=i:c
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1 Comment
Alexandre
on 12 Nov 2013
It would be interesting that the test suite does the assertion on all entries of p1 & p2 in case they return all possible solutions.
assert(all(isprime(p1) & isprime(p2) & (p1+p2==n))
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1 Comment
JD
on 28 Sep 2016
This is a very interesting approach to the problem - learned something new today :D.
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2 Comments
Jamie Sargant
on 1 Jun 2013
I dont understand what the problem with solution is ?
George
on 5 Feb 2014
Your for loop bounds exceed the number of prime factors of n. Also, it looks like you are solving for the stated case n=286 and the test cases are using additional inputs.
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1 Comment
Luigi Sanguigno
on 20 Oct 2012
To compute all possible.. replace b=find(isprime(p2),1,'first'); with b=isprime(p2);
enjoy
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1 Comment
Martin
on 4 Jun 2013
smart and short... i needed a "few" lines more :-)
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2 Comments
Søren
on 2 Jun 2012
Shouldn't pass, but does. No check of both numbers being primenumbers
Ned Gulley
on 21 Jun 2012
I see your point. You were lucky with the original test suite, but I've added a few more test points. Thanks.
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1 Comment
Ze Zhang
on 17 Mar 2015
Nice! I didn't know they have a function for C_n^k before.
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1 Comment
Cris Luengo
on 14 Jul 2012
Sometimes vectorized code is not the shortest.
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