multimap::insert
Inserts an element or a range of elements into a multimap.
// (1) single element
pair<iterator, bool> insert(
const value_type& Val
);
// (2) single element, perfect forwarded
template<class ValTy>
pair<iterator, bool> insert(
ValTy&& Val
);
// (3) single element with hint
iterator insert(
const_iterator Where,
const value_type& Val
);
// (4) single element, perfect forwarded, with hint
template<class ValTy>
iterator insert(
const_iterator Where,
ValTy&& Val
);
// (5) range
template<class InputIterator>
void insert(
InputIterator First,
InputIterator Last
);
// (6) initializer list
void insert(
initializer_list<value_type> IList
);
Parameters
Parameter |
Description |
Val |
The value of an element to be inserted into the multimap. |
Where |
The place to start searching for the correct point of insertion. (If that point immediately precedes Where, insertion can occur in amortized constant time instead of logarithmic time.) |
ValTy |
Template parameter that specifies the argument type that the map can use to construct an element of value_type, and perfect-forwards Val as an argument. |
First |
The position of the first element to be copied. |
Last |
The position just beyond the last element to be copied. |
InputIterator |
Template function argument that meets the requirements of an input iterator that points to elements of a type that can be used to construct value_type objects. |
IList |
The initializer_list from which to copy the elements. |
Return Value
The single-element-insert member functions, (1) and (2), return an iterator to the position where the new element was inserted into the multimap.
The single-element-with-hint member functions, (3) and (4), return an iterator that points to the position where the new element was inserted into the multimap.
Remarks
No pointers or references are invalidated by this function, but it may invalidate all iterators to the container.
During the insertion of just one element, if an exception is thrown, the container's state is not modified. During the insertion of multiple elements, if an exception is thrown, the container is left in an unspecified but valid state.
The value_type of a container is a typedef that belongs to the container, and for map, multimap<K, V>::value_type is pair<const K, V>. The value of an element is an ordered pair in which the first component is equal to the key value and the second component is equal to the data value of the element.
The range member function (5) inserts the sequence of element values into a multimap that corresponds to each element addressed by an iterator in the range [First, Last); therefore, Last does not get inserted. The container member function end() refers to the position just after the last element in the container—for example, the statement m.insert(v.begin(), v.end()); inserts all elements of v into m.
The initializer list member function (6) uses an initializer_list to copy elements into the map.
For insertion of an element constructed in place—that is, no copy or move operations are performed—see multimap::emplace and multimap::emplace_hint.
Example
// multimap_insert.cpp
// compile with: /EHsc
#include <map>
#include <iostream>
#include <string>
#include <vector>
#include <utility> // make_pair()
using namespace std;
template <typename M> void print(const M& m) {
cout << m.size() << " elements: ";
for (const auto& p : m) {
cout << "(" << p.first << ", " << p.second << ") ";
}
cout << endl;
}
int main()
{
// insert single values
multimap<int, int> m1;
// call insert(const value_type&) version
m1.insert({ 1, 10 });
// call insert(ValTy&&) version
m1.insert(make_pair(2, 20));
cout << "The original key and mapped values of m1 are:" << endl;
print(m1);
// intentionally attempt a duplicate, single element
m1.insert(make_pair(1, 111));
cout << "The modified key and mapped values of m1 are:" << endl;
print(m1);
// single element, with hint
m1.insert(m1.end(), make_pair(3, 30));
cout << "The modified key and mapped values of m1 are:" << endl;
print(m1);
cout << endl;
// The templatized version inserting a jumbled range
multimap<int, int> m2;
vector<pair<int, int>> v;
v.push_back(make_pair(43, 294));
v.push_back(make_pair(41, 262));
v.push_back(make_pair(45, 330));
v.push_back(make_pair(42, 277));
v.push_back(make_pair(44, 311));
cout << "Inserting the following vector data into m2:" << endl;
print(v);
m2.insert(v.begin(), v.end());
cout << "The modified key and mapped values of m2 are:" << endl;
print(m2);
cout << endl;
// The templatized versions move-constructing elements
multimap<int, string> m3;
pair<int, string> ip1(475, "blue"), ip2(510, "green");
// single element
m3.insert(move(ip1));
cout << "After the first move insertion, m3 contains:" << endl;
print(m3);
// single element with hint
m3.insert(m3.end(), move(ip2));
cout << "After the second move insertion, m3 contains:" << endl;
print(m3);
cout << endl;
multimap<int, int> m4;
// Insert the elements from an initializer_list
m4.insert({ { 4, 44 }, { 2, 22 }, { 3, 33 }, { 1, 11 }, { 5, 55 } });
cout << "After initializer_list insertion, m4 contains:" << endl;
print(m4);
cout << endl;
}
Output
The original key and mapped values of m1 are:
2 elements: (1, 10) (2, 20)
The modified key and mapped values of m1 are:
3 elements: (1, 10) (1, 111) (2, 20)
The modified key and mapped values of m1 are:
4 elements: (1, 10) (1, 111) (2, 20) (3, 30)
Inserting the following vector data into m2:
5 elements: (43, 294) (41, 262) (45, 330) (42, 277) (44, 311)
The modified key and mapped values of m2 are:
5 elements: (41, 262) (42, 277) (43, 294) (44, 311) (45, 330)
After the first move insertion, m3 contains:
1 elements: (475, blue)
After the second move insertion, m3 contains:
2 elements: (475, blue) (510, green)
After initializer_list insertion, m4 contains:
5 elements: (1, 11) (2, 22) (3, 33) (4, 44) (5, 55)
Requirements
Header: <map>
Namespace: std