Namespaces
Variants
Actions

std::set<Key,Compare,Allocator>::insert

From cppreference.com
< cpp‎ | container‎ | set
 
 
 
std::set
Member functions
          
 
std::pair <iterator, bool> insert( const value_type& value );
(1) (constexpr since C++26)
std::pair <iterator, bool> insert( value_type&& value );
(2) (since C++11)
(constexpr since C++26)
(3)
iterator insert( iterator pos, const value_type& value );
(until C++11)
iterator insert( const_iterator pos, const value_type& value );
(since C++11)
(constexpr since C++26)
iterator insert( const_iterator pos, value_type&& value );
(4) (since C++11)
(constexpr since C++26)
template< class InputIt >
void insert( InputIt first, InputIt last );
(5) (constexpr since C++26)
void insert( std::initializer_list <value_type> ilist );
(6) (since C++11)
(constexpr since C++26)
insert_return_type insert( node_type&& nh );
(7) (since C++17)
(constexpr since C++26)
iterator insert( const_iterator pos, node_type&& nh );
(8) (since C++17)
(constexpr since C++26)
template< class K >
std::pair <iterator, bool> insert( K&& x );
(9) (since C++23)
(constexpr since C++26)
template< class K >
iterator insert( const_iterator pos, K&& x );
(10) (since C++23)
(constexpr since C++26)

Attempts to insert element(s) into *this.

  • If *this already contain an element with an equivalent key, does nothing.
  • Otherwise, inserts the element(s) into *this.
1-4) Inserts value. If pos is provided, value will be inserted as close as possible to the position just prior to pos.
1,3) If value_type is not CopyInsertable into set, the behavior is undefined.
2,4) If value_type is not MoveInsertable into set, the behavior is undefined.
(since C++11)
5) Inserts elements from range [first, last).
If any of the following conditions is satisfied, the behavior is undefined:
(since C++11)
  • first or last is an iterator into *this.
6) Inserts elements from initializer list ilist.
Equivalent to insert(ilist.begin(), ilist.end()).
7) If nh is an empty node handle, does nothing. Otherwise, inserts the element owned by nh into the container , if the container doesn't already contain an element with a key equivalent to nh.key(). The behavior is undefined if nh is not empty and get_allocator() != nh.get_allocator().
8) If nh is an empty node handle, does nothing and returns the end iterator. Otherwise, inserts the element owned by nh into the container, if the container doesn't already contain an element with a key equivalent to nh.key(), and returns the iterator pointing to the element with key equivalent to nh.key()(regardless of whether the insert succeeded or failed). If the insertion succeeds, nh is moved from, otherwise it retains ownership of the element. The element is inserted as close as possible to the position just prior to pos. The behavior is undefined if nh is not empty and get_allocator() != nh.get_allocator().
9,10) Constructs an object u of type value_type with std::forward <K>(x) and then inserts u into *this. The existence of the equivalent key is determined transparently using x before constructing u.
If any of the folllowing conditions is satisfied, the behavior is undefined:
9) This overload participates in overload resolution only if Compare is transparent.
10) u will be inserted as close as possible to the position just prior to pos.
This overload participates in overload resolution only if all following conditions are satisfied:

No iterators or references are invalidated. If the insertion is successful, pointers and references to the element obtained while it is held in the node handle are invalidated, and pointers and references obtained to that element before it was extracted become valid.(since C++17)

Contents

[edit] Parameters

pos - iterator to the position before which the new element will be inserted
value - element value to insert
first, last - the pair of iterators defining the source range of elements to insert
ilist - initializer list to insert the values from
nh - a compatible node handle
x - a value of any type that can be transparently compared with a key
Type requirements
-InputIt must meet the requirements of LegacyInputIterator.

[edit] Return value

1,2) A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool value set to true if and only if the insertion took place.
3,4) An iterator to the inserted element, or to the element that prevented the insertion.
7) An object of insert_return_type with the members initialized as follows:
  • If nh is empty, inserted is false, position is end(), and node is empty.
  • Otherwise if the insertion took place, inserted is true, position points to the inserted element, and node is empty.
  • If the insertion failed, inserted is false, node has the previous value of nh, and position points to an element with a key equivalent to nh.key().
8) End iterator if nh was empty, iterator pointing to the inserted element if insertion took place, and iterator pointing to an element with a key equivalent to nh.key() if it failed.
9) A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool value set to true if and only if the insertion took place.
10) An iterator to the inserted element, or to the element that prevented the insertion.

[edit] Exceptions

If an exception is thrown by any operation during the insertion of a single element, the insertion has no effect.

[edit] Complexity

Given \(\scriptsize N\)N as size():

1,2) \(\scriptsize \log(N)\)log(N)
3,4) Amortized constant if the insertion happens in the position just after(until C++11)before(since C++11) pos, \(\scriptsize \log(N)\)log(N) otherwise.
5,6) \(\scriptsize \log(N + M)\)log(N+M), where \(\scriptsize M\)M is the number of elements to insert.
7) \(\scriptsize \log(N)\)log(N)
8) Amortized constant if the insertion happens in the position just before pos, \(\scriptsize \log(N)\)log(N) otherwise.
9) \(\scriptsize \log(N)\)log(N)
10) Amortized constant if the insertion happens in the position just before pos, \(\scriptsize \log(N)\)log(N) otherwise.

[edit] Notes

The hinted insert ((3,4), (8) and (10)) does not return a boolean in order to be signature-compatible with positional insert on sequential containers, such as std::vector::insert . This makes it possible to create generic inserters such as std::inserter . One way to check success of a hinted insert is to compare size() before and after.

The overloads (5,6) are often implemented as a loop that calls the overload (3) with end() as the hint; they are optimized for appending a sorted sequence (such as another std::set ) whose smallest element is greater than the last element in *this.

If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).

Feature-test macro Value Std Feature
__cpp_lib_associative_heterogeneous_insertion 202311L (C++26) Heterogeneous overloads for the remaining member functions in ordered and unordered associative containers. (9,10)

[edit] Example

Run this code
#include <cassert>
#include <iostream>
#include <set>
 
int main()
{
 std::set <int> set;
 
 auto result_1 = set.insert(3);
 assert (result_1.first != set.end()); // it is a valid iterator
 assert (*result_1.first == 3);
 if (result_1.second)
 std::cout << "insert done\n";
 
 auto result_2 = set.insert(3);
 assert (result_2.first == result_1.first); // same iterator
 assert (*result_2.first == 3);
 if (!result_2.second)
 std::cout << "no insertion\n";
}

Output: 

insert done
no insertion

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 233 C++98 pos was just a hint, it could be totally ignored the insertion is required to
be as close as possible to the
position just prior to pos
LWG 264 C++98 the complexity of overload (5) was required to be linear if
the range [first, last) is sorted according to Compare 		removed the linear requirement
in this special case
LWG 316 C++98 in the return value of overload (1), it was not specified
which bool value indicates a successful insertion 		success is indicated by true

[edit] See also

(C++11)
constructs element in-place
(public member function) [edit]
constructs elements in-place using a hint
(public member function) [edit]
creates a std::insert_iterator of type inferred from the argument
(function template) [edit]

AltStyle によって変換されたページ (->オリジナル) /