unordered_multimap emplace_hint() function in C++ STL
Last Updated :
17 Dec, 2021
The unordered_multimap::emplace_hint() is a built-in function in C++ STL which inserts a new {key:element} in the unordered_multimap container. It starts searching from the position provided in the parameter for the insertion point of the element. The position only acts as a hint, it does not decide the position at which the insertion is to be done. The insertion is done automatically at the position according to the container’s criterion. It increases the size of the container by one.
Syntax:
unordered_multimap_name.emplace_hint(iterator position, key, element)
Parameters: The function accepts three mandatory parameters which are described below:
- position: it specifies the iterator pointing to the position from where search operation for insertion is to be started.
- key: it specifies the key which is to be inserted in the container.
- element: it specifies the element which is to be inserted in the container
Return Value: It returns an iterator that points to the newly inserted element.
Below programs illustrates the above function:
Program 1:
C++
#include <iostream>
#include <string>
#include <unordered_map>
using namespace std;
int main()
{
unordered_multimap< int , int > sample;
auto it = sample.emplace_hint(sample.begin(), 1, 2);
it = sample.emplace_hint(it, 1, 2);
it = sample.emplace_hint(it, 1, 3);
sample.emplace_hint(sample.begin(), 4, 9);
sample.emplace_hint(sample.begin(), 60, 89);
std::cout << "Key and elements:\n" ;
for ( auto it = sample.begin(); it != sample.end(); it++)
cout << "{" << it->first << ":" << it->second << "}\n " ;
std::cout << std::endl;
return 0;
}
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Output:
Key and elements:
{60:89}
{4:9}
{1:2}
{1:2}
{1:3}
Program 2:
C++
#include <iostream>
#include <string>
#include <unordered_map>
using namespace std;
int main()
{
unordered_multimap<string, string> sample;
auto it = sample.emplace_hint(sample.begin(), "gopal" , "dave" );
it = sample.emplace_hint(it, "gopal" , "dave" );
it = sample.emplace_hint(it, "Geeks" , "Website" );
sample.emplace_hint(sample.begin(), "Geeks" , "STL" );
sample.emplace_hint(sample.begin(), "Multimap" , "functions" );
std::cout << "Key and elements:\n" ;
for ( auto it = sample.begin(); it != sample.end(); it++)
cout << "{" << it->first << ":" << it->second << "}\n " ;
std::cout << std::endl;
return 0;
}
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Output:
Key and elements:
{Multimap:functions}
{Geeks:Website}
{Geeks:STL}
{gopal:dave}
{gopal:dave}
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