std::map<Key,T,Compare,Allocator>::insert
std::pair<iterator, bool> insert( const value_type& value ); |
(1) | |
template< class P > std::pair<iterator, bool> insert( P&& value ); |
(2) | (since C++11) |
std::pair<iterator, bool> insert( value_type&& value ); |
(3) | (since C++17) |
(4) | ||
iterator insert( iterator hint, const value_type& value ); |
(until C++11) | |
iterator insert( const_iterator hint, const value_type& value ); |
(since C++11) | |
template< class P > iterator insert( const_iterator hint, P&& value ); |
(5) | (since C++11) |
iterator insert( const_iterator hint, value_type&& value ); |
(6) | (since C++17) |
template< class InputIt > void insert( InputIt first, InputIt last ); |
(7) | |
void insert( std::initializer_list<value_type> ilist ); |
(8) | (since C++11) |
insert_return_type insert( node_type&& nh ); |
(9) | (since C++17) |
iterator insert( const_iterator hint, node_type&& nh ); |
(10) | (since C++17) |
Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key.
value
. The overload
(2) is equivalent to
emplace(std::forward<P>(value))
and only participates in overload resolution if
std::is_constructible<value_type, P&&>::value == true
.
value
in the position as close as possible, just prior
(since C++11), to
hint
. The overload
(5) is equivalent to
emplace_hint(hint, std::forward<P>(value))
and only participates in overload resolution if
std::is_constructible<value_type, P&&>::value == true
.
[first, last)
. If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending
LWG2844).
ilist
. If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending
LWG2844).
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()
.
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
hint
. The behavior is undefined if
nh
is not empty and
get_allocator() != nh.get_allocator()
.
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).
Parameters
hint | - |
|
||||
value | - | element value to insert | ||||
first, last | - | range of elements to insert | ||||
ilist | - | initializer list to insert the values from | ||||
nh | - | a compatible node handle | ||||
Type requirements | ||||||
-InputIt must meet the requirements of LegacyInputIterator. |
Return value
bool
denoting whether the insertion took place.
insert_return_type
with the members initialized as follows:
- If
nh
is empty,inserted
isfalse
,position
isend()
, andnode
is empty. - Otherwise if the insertion took place,
inserted
istrue
,position
points to the inserted element, andnode
is empty. - If the insertion failed,
inserted
isfalse
,node
has the previous value ofnh
, andposition
points to an element with a key equivalent tonh.key()
.
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.
Exceptions
Complexity
O(log(size()))
.
4-6) Amortized constant if the insertion happens in the position just after the hint, logarithmic in the size of the container otherwise. | (until C++11) |
4-6) Amortized constant if the insertion happens in the position just before the hint, logarithmic in the size of the container otherwise. | (since C++11) |
O(N*log(size() + N))
, where N is the number of elements to insert.
O(log(size()))
.
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"; }
Output:
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
See also
(C++11)
|
constructs element in-place (public member function) |
(C++11)
|
constructs elements in-place using a hint (public member function) |
(C++17)
|
inserts an element or assigns to the current element if the key already exists (public member function) |
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