unordered_set::unordered_set

Constructs a container object.

unordered_set(
    const unordered_set& Right
);
explicit unordered_set(
    size_type bucket_count = N0,
    const Hash& Hash = Hash(),
    const Comp& Comp = Comp(),
    const Allocator& Al = Alloc()
);
unordered_set(
    unordered_set&& Right
);
unordered_set(
    initializer_list<Type> IList
);
unordered_set(
    initializer_list<Type> IList, 
    size_type bucket_count
);
unordered_set(
    initializer_list<Type> IList, 
    size_type bucket_count,
    const Hash& Hash
);
unordered_set(
    initializer_list<Type> IList, 
    size_type bucket_count,
    const Hash& Hash,
    const Comp& Comp
);
unordered_set(
    initializer_list<Type> IList, 
    size_type bucket_count,
    const Hash& Hash,
    const Comp& Comp,
    const Allocator& Al
);
template<class InputIterator>
    unordered_set(
    InputIterator first, 
    InputIterator last,
    size_type bucket_count = N0,
    const Hash& Hash = Hash(),
    const Comp& Comp = Comp(),
    const Allocator& Al = Alloc());

Parameters

Remarks

The first constructor specifies a copy of the sequence controlled by Right. The second constructor specifies an empty controlled sequence. The third constructor specifies a copy of the sequence by moving Right The fourth through eighth constructors use an initializer_list to specify the elements to copy. The ninth constructor inserts the sequence of element values [first, last).

All constructors also initialize several stored values. For the copy constructor, the values are obtained from Right. Otherwise:

The minimum number of buckets is the argument bucket_count, if present; otherwise it is a default value described here as the implementation-defined value N0.

The hash function object is the argument Hash, if present; otherwise it is Hash().

The comparison function object is the argument Comp, if present; otherwise it is Comp().

The allocator object is the argument Al, if present; otherwise, it is Alloc().

Example 

Code

/ std_tr1__unordered_set__unordered_set_construct.cpp 
// compile with: /EHsc 
#include <unordered_set> 
#include <iostream> 

using namespace std;

typedef unordered_set<char> Myset;
int main()
{
    Myset c1;

    c1.insert('a');
    c1.insert('b');
    c1.insert('c');

    // display contents " [c] [b] [a]" 
    for (auto& c : c1){
        cout << " [" << c << "]";
    }
    cout << endl;

    Myset c2(8,
        hash<char>(),
        equal_to<char>(),
        allocator<pair<const char, int> >());

    c2.insert('d');
    c2.insert('e');
    c2.insert('f');

    // display contents " [f] [e] [d]" 
    for (auto& c : c2){
        cout << " [" << c << "]";
    }
    cout << endl;

    Myset c3(c1.begin(),
        c1.end(),
        8,
        hash<char>(),
        equal_to<char>(),
        allocator<pair<const char, int> >());

    // display contents " [c] [b] [a]" 
    for (auto& c : c3){
        cout << " [" << c << "]";
    }
    cout << endl;

    Myset c4(move(c3));

    // display contents " [c] [b] [a]" 
    for (auto& c : c4){
        cout << " [" << c << "]";
    }
    cout << endl;

    Myset c5{ { 'a', 'b', 'c' } };

    for (auto& c : c5){
        cout << " [" << c << "]";
    }
    cout << endl;
}

Output

[a] [b] [c]
 [d] [e] [f]
 [a] [b] [c]
 [a] [b] [c]

Requirements

Header: <unordered_set>

Namespace: std

See Also

Reference

<unordered_set>

unordered_set Class