Problem 67. Find common elements in matrix rows

Created by Cody Team

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Given a matrix, find all elements that exist in every row.
For example, given
 A =
     1 2 3 5
     9 2 5 9
     3 2 5 9
     1 2 1 5
     5 1 3 2
the answer would be the vector '2 5'. Elements should be returned sorted ascending.
Note there is no guarantee that there are any such elements; if there are none, the routine should return the empty set. Also, the matrix might contain NaNs, repeats, or very large or very small elements.

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Last Solution submitted on Jul 07, 2025

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Jason Kaeding on 26 Jan 2012

Any version of "empty" should be acceptable as correct.

For example, intersect can output a 1x0 empty matrix. That should be allowed.

Nils on 22 Oct 2013

Somehow the assert is triggered if the function returns a [] that has been "sorted".
If I include that code
if ~isempty(y)
y = sort(unique(y));
end
no assert is triggered. Seem strange!

Toolman Thoolen on 1 Feb 2018

How can the leading solution be 0??

David Verrelli on 25 May 2018

Following many comments, the Test Suite should be amended to check for an empty output vector using "isempty", rather testing for equality to []. Such an amendment is appropriate, and would not break any of the previously submitted successful solutions. —DIV

goc3 on 26 Oct 2020

Test cases with an empty result now test against isempty().

Siddharth on 28 Mar 2024

intresting

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Problem 67. Find common elements in matrix rows

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Problem 67. Find common elements in matrix rows

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Last 200 Solutions

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