std::map insert() method
- since C++17
- since C++11
- until C++11
// (1) Non const version only
std::pair<iterator, bool> insert( const value_type& value );
// (2) Non const version only
template< class P >
std::pair<iterator, bool> insert( P&& value );
// (3) Non const version only
std::pair<iterator, bool> insert( value_type&& value );
// (4) Non const version only
iterator insert( const_iterator hint, const value_type& value );
// (5) Non const version only
template< class P >
iterator insert( const_iterator hint, P&& value );
// (6) Non const version only
iterator insert( const_iterator hint, value_type&& value );
// (7) Non const version only
template< class InputIt >
void insert( InputIt first, InputIt last );
// (8) Non const version only
void insert( std::initializer_list<value_type> ilist );
// (9) Non const version only
insert_return_type insert( node_type&& nh );
// (10) Non const version only
iterator insert( const_iterator hint, node_type&& nh );
// (1) Non const version only
std::pair<iterator, bool> insert( const value_type& value );
// (2) Non const version only
template< class P >
std::pair<iterator, bool> insert( P&& value );
// (4) Non const version only
iterator insert( const_iterator hint, const value_type& value );
// (5) Non const version only
template< class P >
iterator insert( const_iterator hint, P&& value );
// (7) Non const version only
template< class InputIt >
void insert( InputIt first, InputIt last );
// (8) Non const version only
void insert( std::initializer_list<value_type> ilist );
// (1) Non const version only
std::pair<iterator, bool> insert( const value_type& value );
// (4) Non const version only
iterator insert( iterator hint, const value_type& value );
// (7) Non const version only
template< class InputIt >
void insert( InputIt first, InputIt last );
Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key.
-
(1-3) Inserts value. The overload (2) is equivalent to
emplace(std::forward<P>(value))
and only participates in overload resolution ifstd::is_constructible<value_type, P&&>::value == true
. -
(4-6) Inserts value in the position as close as possible, just prior, to hint. The overload (5) is equivalent to
emplace_hint(hint, std::forward<P>(value))
and only participates in overload resolution ifstd::is_constructible<value_type, P&&>::value == true
. -
(7) Inserts elements from range [ first, last ). If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).
-
(8) Inserts elements from initializer list
ilist
. If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844). -
(9) If
nh
is an empty node handle, does nothing. Otherwise, inserts the element owned bynh
into the container, if the container doesn't already contain an element with a key equivalent tonh.key()
. The behavior is undefined ifnh
is not empty andget_allocator() != nh.get_allocator()
. -
(10) If
nh
is an empty node handle, does nothing and returns the end iterator. Otherwise, inserts the element owned bynh
into the container, if the container doesn't already contain an element with a key equivalent ton.key()
, and returns the iterator pointing to the element with key equivalent tonh.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 hint. The behavior is undefined ifnh
is not empty andget_allocator() != nh.get_allocator()
.
- since C++17
- until C++11
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.
Parameters
hint
- since C++11
- until C++11
iterator to the position before which the new element will be insertediterator, used as a suggestion as to where to start the searchvalue
- element value to insertcount
- number of elements to insertfirst
,last
- the range of elements to insertilist
- initializer list to insert the values fromnh
- a compatible node handle
Type requirements
- (7)
InputIt
must meet the requirements ofLegacyInputIterator
.
Return value
- (1-3) Returns a pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a
bool
denoting whether the insertion took place. - (4-6) Returns an iterator to the inserted element, or to the element that prevented the insertion.
- (7-8) (none)
- (9) Returns an
insert_return_type
with the members initialized as follows:- If
nh
is empty,inserted
isfalse
,position
isend()
, andnode
isempty
. - Otherwise if the insertion took place,
inserted
istrue
,position
points to the inserted element, andnode
isempty
. - If the insertion failed,
inserted
isfalse
,node
has the previous value of nh, andposition
points to an element with a key equivalent tonh.key()
.
- If
- (10) 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 tonh.key()
if it failed.
Complexity
- (1-3) Logarithmic in the size of the container - O(log size()).
- (4-6)
- since C++11
- until C++11
Amortized constant if the insertion happens in the position just before the hint, logarithmic in the size of the container otherwise - O(1).Amortized constant if the insertion happens in the position just after the hint, logarithmic in the size of the container otherwise - O(1). - (7-8) O(N * log(size() + N)), where N is the number of elements to insert.
- (9) Logarithmic in the size of the container - O(log size()).
- (10)
Amortized constant if the insertion happens in the position just before the hint - O(1) . Logarithmic in the size of the container otherwise - O(log size()).
Exceptions
- (1-6) If an exception is thrown by any operation, the insertion has no effect.
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Notes
The hinted insert (4-6) 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.
Example
#include <iomanip>
#include <iostream>
#include <map>
#include <string>
using namespace std::literals;
template<typename It>
void printInsertionStatus(It it, bool success)
{
std::cout << "Insertion of " << it->first << (success ? " succeeded\n" : " failed\n");
}
int main()
{
std::map<std::string, float> karasunoPlayerHeights;
// Overload 3: insert from rvalue reference
const auto [it_hinata, success] = karasunoPlayerHeights.insert({"Hinata"s, 162.8});
printInsertionStatus(it_hinata, success);
{
// Overload 1: insert from lvalue reference
const auto [it, success2] = karasunoPlayerHeights.insert(*it_hinata);
printInsertionStatus(it, success2);
}
{
// Overload 2: insert via forwarding to emplace
const auto [it, success] = karasunoPlayerHeights.insert(std::pair{"Kageyama", 180.6});
printInsertionStatus(it, success);
}
{
// Overload 6: insert from rvalue reference with positional hint
const std::size_t n = std::size(karasunoPlayerHeights);
const auto it = karasunoPlayerHeights.insert(it_hinata, {"Azumane"s, 184.7});
printInsertionStatus(it, std::size(karasunoPlayerHeights) != n);
}
{
// Overload 4: insert from lvalue reference with positional hint
const std::size_t n = std::size(karasunoPlayerHeights);
const auto it = karasunoPlayerHeights.insert(it_hinata, *it_hinata);
printInsertionStatus(it, std::size(karasunoPlayerHeights) != n);
}
{
// Overload 5: insert via forwarding to emplace with positional hint
const std::size_t n = std::size(karasunoPlayerHeights);
const auto it = karasunoPlayerHeights.insert(it_hinata, std::pair{"Tsukishima", 188.3});
printInsertionStatus(it, std::size(karasunoPlayerHeights) != n);
}
auto node_hinata = karasunoPlayerHeights.extract(it_hinata);
std::map<std::string, float> playerHeights;
// Overload 7: insert from iterator range
playerHeights.insert(std::begin(karasunoPlayerHeights), std::end(karasunoPlayerHeights));
// Overload 8: insert from initializer_list
playerHeights.insert({{"Kozume"s, 169.2}, {"Kuroo", 187.7}});
// Overload 9: insert node
const auto status = playerHeights.insert(std::move(node_hinata));
printInsertionStatus(status.position, status.inserted);
node_hinata = playerHeights.extract(status.position);
{
// Overload 10: insert node with positional hint
const std::size_t n = std::size(playerHeights);
const auto it = playerHeights.insert(std::begin(playerHeights), std::move(node_hinata));
printInsertionStatus(it, std::size(playerHeights) != n);
}
// Print resulting map
std::cout << std::left << '\n';
for (const auto& [name, height] : playerHeights)
std::cout << std::setw(10) << name << " | " << height << "cm\n";
}
Insertion of Hinata succeeded
Insertion of Hinata failed
Insertion of Kageyama succeeded
Insertion of Azumane succeeded
Insertion of Hinata failed
Insertion of Tsukishima succeeded
Insertion of Hinata succeeded
Insertion of Hinata succeeded
Azumane | 184.7cm
Hinata | 162.8cm
Kageyama | 180.6cm
Kozume | 169.2cm
Kuroo | 187.7cm
Tsukishima | 188.3cm
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