In C++, `std::set`s are a kind of associative container that stores unique elements, and in which the elements themselves are the keys.
Questions tagged [stdset]
294 questions
6
votes
1 answer
Copy std::map to std::set in c++
Is it possible with a STL algorithm to deep copy a std::map values to a std::set?
I don't want to explicitly insert in the new set.
I don't want to explicitly do this:
std::map myMap; //filled with something
std::set…
linello
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5
votes
2 answers
How to do the vector of sets in C++?
I can do a simple array of sets:
set < char > * words = new set < char > [10]
How I can do a vector of sets?
This results in a compiler error:
vector < set< char >> v .
Thank you for answers!
Zhake
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5
votes
1 answer
Using lambda expression as Compare for std::set, when it's inside a vector
I want to use a lambda expression as custom Compare for a std::set of integers. There are many answers on this site explaining how to do this, for example https://stackoverflow.com/a/46128321/10774939. And indeed,
#include
#include…
x432ph
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5
votes
3 answers
Insert a sorted range into std::set with hint
Assume I have a std::set (which is by definition sorted), and I have another range of sorted elements (for the sake of simplicity, in a different std::set object). Also, I have a guarantee that all values in the second set are larger than all the…
penelope
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5
votes
3 answers
Can I insert into a set, all the elements of a vector that matches a condition, in a single line of code
I have a vector of elements. I want to populate a set using the elements of this vector that match a certain condition. Can I do this using one line, or in any way that is more concise than the below?
// given vector v
set s;
for (const…
nappyfalcon
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5
votes
4 answers
limit the size of a std::set
I have a short question about the std::set container. Right now I am feeding my set using the pushback function. Of corse the set becomes larger and larger for every push_back.
I am only intrested in the latest 30 elements or so... The older…
Lumpi
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5
votes
1 answer
How do I update a member in a set of std::pair?
I tried doing this:
std::set< pair > mySet;
// fill the set with something
mySet.find( make_pair(someValueX, someValueY) )->first = newX;
But I get the following error on compilation:
error: assignment of member 'std::pair
Tudor Versoiu
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5
votes
1 answer
How to use emplace() in a std::map whose value is a std::set (map from something to a set)?
The Problem
I have a std::map> named misi. I'm wondering why misi.emplace(2345, {6, 9}); and misi.emplace({2345, {6, 9}}); don't work as expected, as shown below.
The Code
#include // std:set
#include
Siu Ching Pong -Asuka Kenji-
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4
votes
2 answers
Creating the container of smart pointers by cloning elements of another container
I have a class, which supports cloning (via method clone). I have a bunch of its instances in a vector of std::unique_ptr.
Now, I want to create an std::set of same smart pointers from the above vector, ideally during its construction. The obvious…
one_two_three
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4
votes
1 answer
'Candidate template ignored: couldn't infer template argument' with std::set
I'm writing a function to manipulate a set with it's iterators, and it's giving me the error
candidate template ignored: couldn't infer template argument
The minimum reproducible code is as follows:
#include
using namespace…
Gabriel Bergoc
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4
votes
2 answers
How to construct a std::set or Boost flat_set from objects’ data members?
#include
#include
#include
class Myclass
{
int member_a;
int member_b;
public:
Myclass() {};
Myclass(int a_init, int b_init) : member_a(a_init), member_b(b_init) {};
operator int() const { return…
Tim
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4
votes
3 answers
STL way of creating/filling std::set from std::vector
I want to create and fill a set from the contents of a member variable of each entry of a vector. This is what I am doing:
struct S { int i; };
int main()
{
std::vector structPtrs;
// code to fill the above vector
// create set…
CinCout
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4
votes
2 answers
Why does std::(multi)set provide non const iterator methods
Why do the sets (std::set and std::multiset) in the C++ standard library provide non const_iterator methods (set::begin and multiset::begin)?
Access to the keys through iterators is always const. It does not matter if the set itself is const or not.…
Curious
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4
votes
3 answers
set::key_comp vs set::value_comp in C++?
What is the difference between set::key_comp vs set::value_comp in C++? Going to cplusplus.com page there is no significant difference.
Furthermore on set::key_comp & related set::value_comp pages
last sentence is "(...) key_comp and its sibling…
andrew
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4
votes
1 answer
How to find min/max in std::map like in std::set?
Since both set and map are ordered containers, can the min and the max be found in 0(1) time for std::map like in std::set ?
// for std::set
// std::set s;
auto min = *s.begin();
auto max = *s.rbegin();
How do I obtain the max and min in…
nnrales
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