Given a vector x, find the "counting sequence" y.
A counting sequence is formed by "counting" the entries in a given sequence.
For example, the sequence
x = 5, 5, 2, 1, 1, 1, 1, 3
can be read as
Two 5's, one 2, four 1's, one 3
which translates to
y = 2, 5, 1, 2, 4, 1, 1, 3
So y is the counting sequence for x.
For this problem, all elements in the sequences x and y will be in the range from 1 to 9.
Solution Stats
Problem Comments
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12 Comments
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9 older comments
Yuri K
on 16 Feb 2012
The problem does not define correct solution if same number is not in consecutive order, like x = [5 5 2 1 1 5 3]; Should it be three 5's, or two 5's then one 5? If it's an encoding problem the correct solution should be the last, right?
Richard Zapor
on 19 May 2012
Typical DPCM encoding removes the DC and thus starts at 0, not 1. An 11% enhancement in encoding.
Jean-Marie Sainthillier
on 22 Jul 2012
Good problem.
Jean-Marie Sainthillier
on 13 Mar 2013
Most of the solutions with UNIQUE don't work when same number is not in consecutive order.
Alfonso Nieto-Castanon
on 13 Mar 2013
in the new test case 5, with x=[1 2 2 1], the test suite answer is [2 1 2 2] (two 1's, two 2's). I would expect the correct answer to be [1 1 2 2 1 1] (one 1, two 2's, one 1). I guess I am misinterpreting the question?
Jean-Marie Sainthillier
on 14 Mar 2013
No. you are right. The test case 5 is wrong.
Ned Gulley
on 14 Mar 2013
My mistake guys. Sorry about that. By the way, these comments are very helpful for adding (and fixing) bad test cases. Thanks for taking the time to comment.
Santosh Kumar Choudhary
on 28 Sep 2017
Test case 5 answer is wrong. the correct answer is [2 1 2 2]. Change the test case 5 answer
Deepthi Palagati
on 19 Sep 2018
test case 5 answer is wrong
Hans Kramer
on 23 Oct 2018
Just to clarify: test case 5 isnt wrong.
Sanzhar Askaruly
on 7 Jul 2019
wow, last test case is so fun!
Bryan Lambo
on 6 Jan 2020
This only took me a few minutes until I saw Case 5 haha! Fun and mind boggling
Solution Comments
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4 Comments
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1 older comment
Jean-Marie Sainthillier
on 13 Mar 2013
Smart !
Doesn't work with [1 2 2 1] for example.
Ned Gulley
on 13 Mar 2013
Thanks for the additional test question!
Santosh Kumar Choudhary
on 28 Sep 2017
Test case 5 answer is wrong. the correct answer is [2 1 2 2]. Change the test case 5 answer
VISHWATEJ N
on 2 Aug 2019
i need the code part of 3rd test case ..
can anyone help
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2 Comments
Aurelien Queffurust
on 21 Feb 2012
does not work if numbers have 2 digits , for example : if x = [1 5 8 9 15 14 8 15]
Peter Wittenberg
on 29 Mar 2012
Yes, it only works for 1 to 9, but that is what the problem specified. It is a good solution.
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1 Comment
Andrew Newell
on 13 Jun 2013
Solutions like this look much more elegant to me than the regexp expressions; and although using 'ans' would shorten it slightly, who would do that in serious code?
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