Problem 1096. Largest Twin Primes

Created by Des Mc Manus

Solve Later

{"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","targetMode":"","relationshipId":"rId1","target":"/matlab/document.xml"},{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/output","targetMode":"","relationshipId":"rId2","target":"/matlab/output.xml"}],"parts":[{"partUri":"/matlab/document.xml","relationship":[],"contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:hyperlink w:docLocation=\"http://en.wikipedia.org/wiki/Twin_prime\"><w:r><w:t>Twin primes</w:t></w:r></w:hyperlink><w:r><w:t> are primes p1, p2 = p1 + 2 such that both p1 and p2 are prime numbers. Given a positive integer N (&gt;=5) what are the largest twin primes (in order) &lt;= N. For example, if N = 20 then p1 = 17 and p2 = 19.</w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

Solve

Solution Stats

376 Solutions
229 Solvers

Last Solution submitted on Sep 19, 2020

Last 200 Solutions

Solution Comments

Solution 551414

1 Comment

1 Comment

Mattias on 1 Jan 2015

Was able to reduce size a few times and finally got to this solution by borrowing tricks used by Grzegorz Knor and Dan.

Solution 173238

2 Comments

2 Comments

Ryan on 5 Dec 2012

Tim,
Can you explain what the +'01'-'0' is doing? I don't see how i+'01'-'0'=[i,i+1].
Thanks

J.R.! Menzinger on 6 Dec 2012

'01 ' is a char vector of 2 positions: '0' ans '1'.
If you subtract '0' to it, it results a char vector with characters 0 and 1.
So '01'-'0' is the same as [0 1], but because of the '[]', it cost less operations.

Problem Recent Solvers229

Problem Tags

primes