Problem 1237. It's race time! Write a faster function than the test suite call of unique().

Created by Jeremy

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Write a function to get unique elements of a vector faster than unique()! Input will be a vector (of integers or floating point numbers) of any size. The order of the returned vector is unimportant.

Example: Input: x = [1 1 2 2 3 3]; Output: [1 2 3];

Input: x = [0.1 3.1 2.1 2.0 3.1]; Output: [0.1 3.1 2.1 2.0]; % or any order

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Last Solution submitted on Oct 31, 2023

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Jeremy on 1 Feb 2013

I'm sure some smarter person will find a faster method!

Muthu Annamalai on 2 Feb 2013

My solution passed on the third try; there's definitely some CPU timing mismatch going on!

Jeremy on 3 Feb 2013

Agreed, some of my solutions passed only part of the time.

Jeremy on 3 Feb 2013

Hi, just wondering whether someone could help me out here. I was expanding the testset, and I was trying x = [1:10 2:11] but I got an error "Error: Dimensions of matrices being concatenated are not consistent." I then tried x = [1 2 3 4], and x = 1:4; but got the same error. On my version of MATLAB all these statements work perfectly and I believe they are basic MATLAB syntax. x = [1; 2; 3; 4] worked fine however. In the end I had to transpose the matrices.

Jeremy

shen on 27 Dec 2013

it even cannot pass on my own computer, but....

Rafael S.T. Vieira on 17 Sep 2020

Jeremy, please increase the size of the third case. Performance tests are not made with small samples (unless they are run several times)...because many other factors may affect the time (alternating processes, server overload, memory usage, etc). A regular CPU is always multi-tasking.

Rafael S.T. Vieira on 17 Sep 2020

About your problem with arrays, try adding a comma between lists.

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Problem 1237. It's race time! Write a faster function than the test suite call of unique().

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Problem 1237. It's race time! Write a faster function than the test suite call of unique().

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