Problem 44341. Hexagonal numbers on a spiral matrix

Created by Mehmet OZC

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:r><w:t>Put hexagonal numbers in a ( m x m ) spiral matrix and return the sum of its diagonal elements.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Formula of hexagonal numbers h(n) = 2n^2 - n</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>If m = 5;</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[spiral(5) =   \n  21    22    23    24    25\n  20     7     8     9    10\n  19     6     1     2    11\n  18     5     4     3    12\n  17    16    15    14    13]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>First 5x5=25 hexagonal numbers are;</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[h = [1 6 15 28 45 66 91 120 153 190 231 276 325 378 435 496 561 630 703 780 861 946 1035 1128 1225]]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>We put them in a spiral format;</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[   spiralHex = [\n861  946  1035  1128  1225\n780  91  120  153  190\n703  66  1  6  231\n630  45  28  15  276\n561  496  435  378  325]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>And sum its diag = 861 + 91 + 1 + 15 + 325 = 1293.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Return the output as char.</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

503 Solutions
94 Solvers

Last Solution submitted on Sep 27, 2021

Last 200 Solutions

Problem Comments

Solution Comments

Solution 1330565

4 Comments

4 Comments

Show 1 older comment

Angelo Gelmini on 7 Nov 2017

I am not able to figure out why the solutions of my code to test 8 and 9 are wrong.
My wrong results:
- test 8 -> '1250000041666667776'
- test 9 -> '13107200170666672128'

Heiko on 15 Nov 2017

I get precisely the same results as Angelo...

Mehmet OZC on 16 Nov 2017

Angelo and Heiko, your solutions are working to a degree. However to obtain exact results on big numbers you have to use different tools. You can search for uint64 and bigdecimal. Hope it helps.

Hans Kramer on 3 Dec 2018

Thanks for the tip with uint64.

Solution 1305838

2 Comments

2 Comments

Mehmet OZC on 21 Oct 2017

First line is adopted from James's solution: https://www.mathworks.com/matlabcentral/cody/problems/2455-diagonal-of-a-spiral-matrix/solutions/1239477

James on 2 Nov 2017

I was just happy I could use "diag" and "spiral" in this problem, but it's always nice to see some of my solutions get used in other code.

Problem Recent Solvers94

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 44341. Hexagonal numbers on a spiral matrix

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers94

Suggested Problems

More from this Author75

Problem Tags

Community Treasure Hunt

Problem 44341. Hexagonal numbers on a spiral matrix

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers94

Suggested Problems

More from this Author75

Problem Tags

Community Treasure Hunt

Players