Problem 2456. remove single elements

Created by rifat

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Given a vector of integers, remove the elements that have appeared only once. The output elements should be in exact order as the input except the single elements being removed.
Example:
Input: vec = [2 2 1 2 3 4 1 2];
Output: [2 2 1 2 1 2];
Loops are not allowed.

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Last Solution submitted on Nov 11, 2025

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Guillaume on 21 Jul 2014

Since matlab has so many different ways of representing the empty set, could you test for emptiness using isempty(...) rather than isequal([], ...) ?

shahriar memaran on 25 Mar 2017

Test suit # 4 should not compare out = [] with output of the function but rather isempty(out) !!!

Christian Schröder on 21 Oct 2022

Two requests:

1. Please don't add intentional infinite loops to the test suite.
2. Please take more care when scanning for forbidden keywords. "x(grouptransform(x', x', @numel) > 1)" would be a perfectly good solution, but fails the test suite because "grouptransform" contains the letters "for".

Thanks.

Dyuman Joshi on 22 Oct 2022

Test suite has been updated -

The infinite loop has been cleared out, scanning for 'for' loop has been modified and empty sets will now be verified using isempty().

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Problem 2456. remove single elements

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Problem 2456. remove single elements

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