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Questions tagged [stl-algorithm]

STL algorithms is a collection of algorithms defined as template functions in the header of C++'s standard library. These functions are designed to work with ranges of elements usually in the form of iterators. They are designed to be flexible and reusable, encompass a wide scope of functionality, and adhered to certain performance guarantees.

STL algorithms is a collection of algorithms defined as template functions in the <algorithm> header of the C++ standard library. These functions are designed to work with ranges of elements usually in the form of iterators. They are designed to be flexible and reusable, encompass a wide scope of functionality, and adhered to certain performance guarantees.

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std::next_permutation Implementation Explanation

I was curious how std:next_permutation was implemented so I extracted the the gnu libstdc++ 4.7 version and sanitized the identifiers and formatting to produce the following demo... #include #include #include using…
Andrew Tomazos
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How to find the intersection of two STL sets?

I have been trying to find the intersection between two std::set in C++, but I keep getting an error. I created a small sample test for this #include #include #include #include using namespace std; int main()…
ILikeTacos
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Why is there no transform_if in the C++ standard library?

A use case emerged when wanting to do a contitional copy (1. doable with copy_if) but from a container of values to a container of pointers to those values (2. doable with transform). With the available tools I can't do it in less than two steps :…
Nikos Athanasiou
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What is the difference between std::transform and std::for_each?

Both can be used to apply a function to a range of elements. On a high level: std::for_each ignores the return value of the function, and guarantees order of execution. std::transform assigns the return value to the iterator, and does not guarantee…
bendervader
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Why are std::shuffle methods being deprecated in C++14?

According to the cppreference.com reference site on std::shufle, the following method is being deprecated in c++14: template< class RandomIt > void random_shuffle( RandomIt first, RandomIt last ); Why will we no longer be able to call the following…
Trevor Hickey
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Using local classes with STL algorithms

I have always wondered why you cannot use locally defined classes as predicates to STL algorithms. In the question: Approaching STL algorithms, lambda, local classes and other approaches, BubbaT mentions says that 'Since the C++ standard forbids…
David Rodríguez - dribeas
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Composability of STL algorithms

The STL algorithms are a pretty useful thing in C++. But one thing that kind of irks me is that they seem to lack composability. For example, let's say I have a vector> and want to transform that to a vector containing only the…
Sven
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How to use std::find/std::find_if with a vector of custom class objects?

I have a class representing a user called Nick and I want to use std::find_if on it, where I want to find if the userlist vector has an object included with the same username I pass in. I did a few attempts by trying to create a new Nick object for…
Speed
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What does std::includes actually do?

From the standard, std::includes: Returns: true if [first2, last2) is empty or if every element in the range [first2, last2) is contained in the range [first1, last1). Returns false otherwise. Note: as this is under [alg.set.operations], the…
Justin
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C++ implementation explained

When I like to know how a algorithm in the C++ Standard Library could be implemented, I always look at http://en.cppreference.com/w/cpp/algorithm, which is a great source. But sometimes I don't understand some implementation details and I would need…
Christian Ammer
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How to remove duplicates from unsorted std::vector while keeping the original ordering using algorithms?

I have an array of integers that I need to remove duplicates from while maintaining the order of the first occurrence of each integer. I can see doing it like this, but imagine there is a better way that makes use of STL algorithms better? The…
WilliamKF
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Uniform initialization by tuple

Today, I arrived at a situation, where I have a vector of tuples, where the tuples might contain several entries. Now I wanted to convert my vector of tuples to a vector of objects, such that the entries of the tuples will exactly match the uniform…
Aleph0
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What's the difference between std::partial_sum and std::inclusive_scan?

While reading about std::inclusive_scan, there does not appear to be any examples. It strikes me as very similar to std::partial_sum. partial_sum: template< class InputIt, class OutputIt > OutputIt partial_sum( InputIt first, …
Trevor Hickey
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std::copy n elements or to the end

I would like to copy up to N elements. template< class InputIt, class Size, class OutputIt> OutputIt myCopy_n(InputIt first, InputIt last, Size count, OutputIt result) { Size c = count; while (first != last && c > 0) { *result++ =…
aivision2020
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How can I convert std::vector to a vector of pairs std::vector> using an STL algorithm?

I have a vector of integers: std::vector values = {1,2,3,4,5,6,7,8,9,10}; Given that values.size() will always be even. I simply want to convert the adjacent elements into a pair, like this: std::vector> values = { {1,2},…
dev-here
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