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
4
votes
2 answers
std::set custom comparator for 2D points
I need a list of non-duplicated 2D points, so I use a std::set with a custom comparison function. The function I use has problems after inserting points because sometimes the std::find does not find the already inserted points.
const double…
JordiS
- 43
- 5
4
votes
3 answers
Modifying elements in std::set
I have the following code -:
int main()
{
set s;
s.insert( "asas" );
s.insert( "abab" );
for ( auto item : s )
{
cout << item << "\n";
reverse( item.begin(), item.end() );
}
cout << "\n";
…
Anmol Singh Jaggi
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4
votes
1 answer
write-write data race from a std::set insert() and find()?
To experiment with the thread-sanitizer, I created a tiny C++ program which by purpose contains a data race. Indeed, tsan does detect the error, great! However I am puzzled by the generated message...
It reports a write-write data race, where I…
Jos v E
- 165
- 1
- 5
4
votes
1 answer
C++ std::set unable to use operator + on iterator because compilation error
So I encountered a weird iterator bug ONLY on std::set : I'm unable to do a simple thing like (it + 1) on an iterator without a compilation error
Try to compile this yourself :
void setBug()
{
std::set values;
for (auto it =…
Power78
- 311
- 4
- 12
4
votes
1 answer
Comparing two sets of std::weak_ptr
I am trying to compare two sets of C++11 weak_ptr using GCC 4.7.2. The code below shows the smallest possible sample reproducing the error:
std::set, std::owner_less > > set1;
std::set,…
Hans
- 2,448
- 2
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- 30
3
votes
1 answer
MSVC: C++14: std:set: comparison function: why "const" is required?
Sample code:
#include
#include
using namespace std;
class x
{
private:
int i;
public:
int get_i() const { return i; }
};
struct x_cmp
{
bool operator()(x const & m1, x const & m2)
#if _MSC_VER
const
#endif
{
…
pmor
- 5,392
- 4
- 17
- 36
3
votes
1 answer
Why is inserting sorted keys into std::set so much faster than inserting shuffled keys?
I was accidentally surprised to found that inserting sorted keys into std::set is much much faster than inserting shuffled keys. This is somewhat counterintuitive since a red-black tree (I verified that std::set is implemented as a red-black tree on…
Leon Cruz
- 345
- 3
- 11
3
votes
2 answers
How to move a non-copyable element from std::set to std::map using extract?
Consider the following:
#include
#include
Sprite
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3
votes
1 answer
Merge two constant `std::set`s in declaration (not in run-time)
I am trying to elegantly declare a constant std::set object that would be a merger of two other constant std::set objects.
#include
const std::set set_one = { 1,2,3 };
const std::set set_two = { 11,15 };
const std::set set_all…
Regus Pregus
- 560
- 3
- 12
3
votes
1 answer
C2676: binary '<': 'const _Ty' does not define this operator or a conversion to a type acceptable to the predefined operator
I keep getting this error for the code below.
Upon reading this, I believed my error to be the it++ in my for loop, which I tried replacing with next(it, 1) but it didn't solve my problem.
My question is, is the iterator the one giving me the issue…
mlai
- 63
- 1
- 1
- 4
3
votes
4 answers
Does set::insert saves a copy or a pointer C++
does the function set::insert saves a pointer to the element or a copy of it. meaning, can I do the following code, or I have to make sure that the pointers are not deleted?
int *a;
*a=new int(1);
set _set;
_set.insert (*a);
delete a;
*a=new…
SIMEL
- 8,745
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- 130
3
votes
3 answers
std::set operations with custom comparator
I have a question. When I'm using a std::set with custom comparator, other operations like erase or count doesn't work properly.
For example:
int sz(int const & n) {
return __builtin_popcount(n);
}
struct comp {
bool operator()(int const & a,…
Nikita Voloshin
- 55
- 1
- 8
3
votes
1 answer
3
votes
1 answer
Custom Functor in std::set
#include
#include
#include
using namespace std;
int order[26];
struct lexcmp
{
bool operator()(const string &s1,const string &s2)
{
int i=0;
int j=min(s1.size(),s2.size());
while(1)
…
Crosk Cool
- 664
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- 27
3
votes
2 answers
how to convert std::vector to std::set without losing the order
I am using the below code for conversion:
std::set s(v.begin(), v.end());
However, I need to keep the order of the vector elements. How can I do this?
eaytan
- 319
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