Problem 40. Reverse Run-Length Encoder

Created by Cody Team

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{"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>Given a \"counting sequence\" vector x, construct the original sequence y.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>A counting sequence is formed by \"counting\" the entries in a given sequence. This is sometimes called run-length encoding.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>For example, the sequence</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ x = 2, 5, 1, 2, 4, 1, 1, 3]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>can be read as</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ Two 5's, one 2, four 1's, one 3]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>which translates to</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[ y = 5, 5, 2, 1, 1, 1, 1, 3]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>So y is the reconstructed vector that corresponds to the counting sequence x.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>For this problem, all elements in the sequences x and y will be in the range from 1 to 9.</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>"}]}

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2537 Solutions
1801 Solvers

Last Solution submitted on Sep 15, 2020

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Carl Witthoft on 17 Nov 2015

See my function "seqle" on FileExchange. It may not be as compact, but it's easy to use and both encodes and decodes.

David Verrelli on 28 Sep 2017

The problem statement would have been clearer if the principle of RLE had been explained with an encoding example first. Alternatively, it would have been useful to explicitly mention that the data in vector x is being read pairwise.

Sanzhar Askaruly on 5 Jul 2019

easy

subbarao satha on 2 Mar 2020

useful challenge

Solution Comments

Solution 2177272

1 Comment

1 Comment

Tommy on 27 Mar 2020

ugly but more fun than loops!

Solution 668373

1 Comment

1 Comment

Alfonso Nieto-Castanon on 9 May 2015

note: repelem did not exist back when this problem was created

Solution 550698

1 Comment

1 Comment

Diego on 30 Dec 2014

not limited to 1-9

Solution 529550

2 Comments

2 Comments

Adr Paw on 11 Aug 2016

This is my favourite

DJHuang on 2 Mar 2020

NICE

Solution 54224

2 Comments

2 Comments

Jon on 4 Dec 2013

Best score without regexp

bainhome on 8 May 2015

agree,great indeed!

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Problem 40. Reverse Run-Length Encoder

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Problem 40. Reverse Run-Length Encoder

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