C++ multimap - insert() Function
The C++ multimap::insert function is used to insert new elements in the container. This results into increasing the multimap size by the number of elements inserted.
Syntax
//single element version iterator insert (const value_type& val); //single element with hint version iterator insert (iterator position, const value_type& val); //range version template <class InputIterator> void insert (InputIterator first, InputIterator last);
//single element version iterator insert (const value_type& val); template <class P> pair<iterator,bool> insert (P&& val); //single element with hint version iterator insert (const_iterator position, const value_type& val); template <class P> iterator insert (const_iterator position, P&& val); //range version template <class InputIterator> void insert (InputIterator first, InputIterator last); //initializer list version void insert (initializer_list<value_type> il);
Parameters
position |
Specify the hint for the position where the element can be inserted. |
val |
Specify the value to be copied (or moved) to the inserted elements. |
first |
Specify the starting position of InputIterator. Copies of the elements in the range [first,last) are inserted in the container. |
last |
Specify the last position of InputIterator. Copies of the elements in the range [first,last) are inserted in the container. |
il |
Specify the initializer_list object. |
Return Value
Returns an iterator pointing to newly inserted element in the multimap.
Time Complexity
- Logarithmic i.e, Θ(log(n)) if a single element is inserted, but constant i.e, Θ(1) if position provided is optimal.
- Multiple elements insertion: Linearithmic: number of elements inserted multiplied by log of (container size + number of elements inserted). But, in C++ 98, it is linear in (container size + number of elements inserted), if the elements are already sorted.
Example:
In the example below, the multimap::insert function is used to insert elements in the given multimap.
#include <iostream>
#include <map>
using namespace std;
int main (){
multimap<string, string> MMap;
multimap<string, string>::iterator it;
//populating multimap
MMap.insert(pair<string, string>("CAN", "Montreal"));
MMap.insert(pair<string, string>("IND", "Mumbai"));
MMap.insert(pair<string, string>("USA", "New York"));
cout<<"MMap contains: \n ";
for(it = MMap.begin(); it != MMap.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n ";
//insert single element in the multimap
MMap.insert(pair<string, string>("IND", "Delhi"));
cout<<"\nMMap contains: \n ";
for(it = MMap.begin(); it != MMap.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n ";
//insert single element with hint in the multimap
it = MMap.begin();
MMap.insert(it, pair<string, string>("USA", "Washington"));
cout<<"\nMMap contains: \n ";
for(it = MMap.begin(); it != MMap.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n ";
return 0;
}
The output of the above code will be:
MMap contains: CAN Montreal IND Mumbai USA New York MMap contains: CAN Montreal IND Mumbai IND Delhi USA New York MMap contains: CAN Montreal IND Mumbai IND Delhi USA Washington USA New York
Example:
A range of elements can also be inserted into a multimap. Consider the example below.
#include <iostream>
#include <map>
using namespace std;
int main (){
multimap<string, string> MMap1;
multimap<string, string> MMap2;
multimap<string, string>::iterator it;
//populating MMap1
MMap1.insert(pair<string, string>("CAN", "Montreal"));
MMap1.insert(pair<string, string>("IND", "Mumbai"));
MMap1.insert(pair<string, string>("USA", "New York"));
//populating MMap2
MMap2.insert(pair<string, string>("IND", "Delhi"));
MMap2.insert(pair<string, string>("USA", "Washington"));
cout<<"MMap1 contains: \n ";
for(it = MMap1.begin(); it != MMap1.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n ";
//inserts a range of elements from MMap2 to MMap1
MMap1.insert(MMap2.begin(), MMap2.end());
cout<<"\nMMap1 contains: \n ";
for(it = MMap1.begin(); it != MMap1.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n ";
return 0;
}
The output of the above code will be:
MMap1 contains: CAN Montreal IND Mumbai USA New York MMap1 contains: CAN Montreal IND Mumbai IND Delhi USA New York USA Washington
Example:
Similarly, the initializer list version can be used to insert elements in the given multimap.
#include <iostream>
#include <map>
using namespace std;
int main (){
multimap<string, string> MMap;
multimap<string, string>::iterator it;
//populating MMap
MMap.insert(pair<string, string>("CAN", "Montreal"));
MMap.insert(pair<string, string>("IND", "Mumbai"));
MMap.insert(pair<string, string>("USA", "New York"));
cout<<"MMap contains: \n ";
for(it = MMap.begin(); it != MMap.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n ";
//insert elements of initializer list into multimap
initializer_list<pair<const string, string>> ilist =
{{"IND", "Delhi"}, {"USA", "Washington"}};
MMap.insert(ilist);
cout<<"\nMMap contains: \n ";
for(it = MMap.begin(); it != MMap.end(); ++it)
cout<<it->first<<" "<<it->second<<"\n ";
return 0;
}
The output of the above code will be:
MMap contains: CAN Montreal IND Mumbai USA New York MMap contains: CAN Montreal IND Mumbai IND Delhi USA New York USA Washington
❮ C++ <map> Library
