HASH | Notion

unordered_set();

| template< class Key, class Hash = std::hash<Key>, class KeyEqual = std::equal_to<Key>, class Allocator = std::allocator<Key>

> class unordered_set;	(1)	(since C++11)
namespace pmr {
template<
class Key,
class Hash = std::hash<Key>,
class Pred = std::equal_to<Key>
> using unordered_set = std::unordered_set<Key, Hash, Pred,
std::pmr::polymorphic_allocator<Key>>;
}

#include <iostream>
#include <unordered_set>
 
void print(const auto& set)
{
    for (const auto& elem : set)
        std::cout << elem << ' ';
    std::cout << '\\n';
}
 
int main()
{
    std::unordered_set<int> mySet{2, 7, 1, 8, 2, 8}; // creates a set of ints
    print(mySet);
 
    mySet.insert(5); // puts an element 5 in the set
    print(mySet);
 
    if (auto iter = mySet.find(5); iter != mySet.end())
        mySet.erase(iter); // removes an element pointed to by iter
    print(mySet);
 
    mySet.erase(7); // removes an element 7
    print(mySet);
}