C++ Library - <set>


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Introduction

A set is an Associative container which contains a sorted set of unique objects of type Key. Each element may occur only once, so duplicates are not allowed.

There are four kind of Associative containers: set, multiset, map and multimap.

The value of the elements in a set cannot be modified once in the container, i.e., the elements are always const. But they can be inserted or removed from the container.

set containers are generally slower than unordered_set containers in accessing individual elements by their key, but they allow the direct iteration on subsets based on their order.

Definition

Below is definition of std::set from <set> header file

template < 
    class Key,
    class Compare = std::less<Key>,
    class Allocator = std::allocator<Key>
> class set;

Parameters

  • Key − Type of the element contained.

    Key may be substituted by any other data type including user-defined type.

Member types

Following member types can be used as parameters or return type by member functions.

S.N. Member types Definition
1 key_type Key
2 value_type Key
3 reference Allocator::reference

value_type&

4 const_reference Allocator::const_reference

const value_type&

5 pointer Allocator::pointer

std::allocator_traits<Allocator>::pointer

6 const_pointer Allocator::const_pointer

std::allocator_traits<Allocator>::const_pointer

7 iterator BidirectionalIterator
8 const_iterator constant BidirectionalIterator
9 reverse_iterator std::reverse_iterator <iterator>
10 const_reverse_iterator std::reverse_iterator <const_iterator>
11 size_type Unsigned Integer Type (std::size_t)
12 difference_type Signed Integer Type (std::ptrdiff_t)
13 key_compare Compare
14 value_compare Compare
15 allocator_type Allocator

Functions from <set>

Below is list of all methods from <set> header.

MEMBER FUNCTIONS

DEFAULT MEMBER FUNCTIONS

S.N. Method & Description
1 Default constructor

Constructs the set container.

2 Range constructor

Constructs the set container with contents of the range.

3 Copy constructor

Constructs the set container with the copy of other set.

4 Move constructor

Constructs the set container with the contents of other set using move semantics.

5 Initializer-list constructor

Constructs the set container with contents of the inializer list.

6 (destructor)

Destructs the set container.

7 operator=

Assigns values to the set container.

ITERATORS

S.N. Method & Description
1 set::begin

Returns the iterator to beginning.

2 set::cbegin

Returns the const iterator to beginning.

3 set::end

Returns the iterator to end.

4 set::cend

Returns the const iterator to end.

5 set::rbegin

Returns the reverse iterator to reverse beginning.

6 set::crbegin

Return const reverse iterator to reverse beginning.

7 set::rend

Returns the reverse iterator to reverse end.

8 set::crend

Returns the const reverse iterator to reverse end.

CAPACITY

S.N. Method & Description
1 set::empty

Returns wheteher the set container is empty.

2 set::size

Returns the number of elements in the set container.

3 set::max_size

Returns the maximum number of elements that the set container can hold.

MODIFIERS

S.N. Method & Description
1 set::clear

Removes all elements from the set container.

2 set::insert

Inserts new element in the set container.

3 set::emplace

Inserts new element in the set, if its unique.

4 set::emplace_hint

Inserts new element in the set, if its unique, with a hint on the inserting position.

5 set::erase

Removes either a single element or a range of elements from the set container.

6 set::swap

Exchanges the content of the container by the content of another set container of the same type.

LOOKUP

S.N. Method & Description
1 set::count

Returns the number of elements with matching value in the set container.

2 set::find

Searches the set container for value and returns an iterator to it if found, else returns an iterator to set::end.

3 set::lower_bound

Returns an iterator pointing to the first element in the set container which is not considered to go before value.

4 set::upper_bound

Returns an iterator pointing to the first element in the set container which is considered to go after value.

5 set::equal_range

Returns the bounds of a range that includes all the elements in the set container that are equivalent to value.

OBSERVERS

S.N. Method & Description
1 set::key_comp

Returns a copy of the comparison object used by the set container.

2 set::value_comp

Returns a copy of the comparison object used by the set container.

ALLOCATOR

S.N. Method & Description
1 set::get_allocator

Returns a copy of the allocator object associated with the set container.



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