C++ Multiset emplace_hint()

C++ Multiset emplace_hint() function is used to extend the multiset container by inserting new elements into the container using hint as a position for element. Elements are built directly (neither copied nor moved).

The constructor of the element is called by giving the arguments args passed to this function.

Syntax

template <class... Args>
    iterator emplace_hint (const_iterator position, Args&&... args);  //since C++ 11

Parameter

args: The arguments forwarded to construct an element to be inserted into the container.

position: Hint for the position to insert the new elements.

Return value

emplace_hint() function returns an iterator to the newly inserted elements. If element is already exists, insertion is failed and returns iterator to the existing element.

Complexity

If position is not specified then complexity will be logarithmic in container size.

If position is given then complexity will be amortized constant.

Iterator validity

No changes.

Data Races

The container is modified.

Iterating ranges in the container is not safe although concurrently accessing exiting elements is safe.

Exception Safety

If an exception is thrown, there are no changes in the container.

Example 1

Let's see the simple example to insert the elements into the multiset:

#include <iostream>
#include <set>

using namespace std;

int main(void) {
   multiset<int> m = {30, 20, 30, 10};
            
   m.emplace_hint(m.end(), 40);
   m.emplace_hint(m.begin(), 20);

   cout << "Multiset contains following elements" << endl;

   for (auto it = m.begin(); it != m.end(); ++it)
      cout << *it<< endl;

   return 0;
}

Output:

Multiset contains following elements
10
20
20
30
30
40

In the above example, it simply inserts the element into the multiset m with the given value in the given positions.

Example 2

Let's see a simple example:

#include <set>  
#include <string>  
#include <iostream>  
  
using namespace std;  
  
template <typename M> void print(const M& m) {  
    cout << m.size() << " elements: " << endl;  
  
    for (const auto& p : m) {  
        cout << p << "  " ;  
    }  
  
    cout << endl;  
}  
  
int main()  
{  
    multiset<string> m1;  
  
    // Emplace some test data  
    m1.emplace("Ram");  
    m1.emplace("Deep");  
    m1.emplace("Sunil");  
  
    cout << "multiset starting data: ";  
    print(m1);  
    cout << endl;  
  
    // Emplace with hint  
    // m1.end() should be the "next" element after this emplacement  
    m1.emplace_hint(m1.end(), "Deep");  
  
    cout << "multiset modified, now contains ";  
    print(m1);  
    cout << endl;  

return 0;

}

Output:

multiset starting data: 3 elements: 
Deep  Ram  Sunil  

multiset modified, now contains 4 elements: 
Deep  Deep  Ram  Sunil

Example 3

Let's see a simple example to insert the elements into the multiset with the given position:

#include <iostream>
#include <set>

using namespace std;

int main ()
{
  multiset<char> mymultiset;
  auto it = mymultiset.end();

  it = mymultiset.emplace_hint(it,'b');
  mymultiset.emplace_hint(it,'a');
  mymultiset.emplace_hint(mymultiset.end(),'b');

  cout << "mymultiset contains:";
  for (auto& x: mymultiset)
    cout << " [" << x << ']';
    cout << '\n';

  return 0;
}

Output:

mymultiset contains: [a] [b] [b]

Example 4

Let's see a simple example to insert the element:

#include <iostream>
#include <set>
#include <string>

using namespace std;

int main() {

  typedef multiset<string> city;  
   string name;
   city fmly ;
   int n;

   cout<<"Enter the number of family members :";
   cin>>n;

   cout<<"Enter the name of each member: \n";
   for(int i =0; i<n; i++)
   {
       cin>> name;      // Get key

       fmly.emplace_hint(fmly.begin(),name);
       
   }
   
      cout<<"\nTotal members of family is:"<< fmly.size();

      cout<<"\nDetails of family members: \n";
      cout<<"\nName \n ________________________\n";
      city::iterator p;
      for(p = fmly.begin(); p!=fmly.end(); p++)
      {
          cout<<(*p) <<" \n ";
      }
    
   return 0;
}

Output:

Enter the number of fmly members : 4
Enter the name of each member: 
Deep
Sonu
Ajeet
Bob

Total memnber of fmly is:4
Details of fmly members: 

Name 
 ________________________
 Ajeet 
 Bob 
 Deep 
 Sonu

In the above example, it simply inserts the elements by the user's choice in the beginning of multiset.

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