C++ unordered_multiset - emplace_hint() Function

The C++ unordered_multiset::emplace_hint function is used to insert a new element in the unordered_multiset with the hint of insertion position. The insertion of the new element increases the size of the unordered_multiset by one.

The hint is only used to speed up the insertion process considering the actual insertion point is either specified position or close to it.

Syntax

C++11

template <class... Args>
iterator emplace_hint (const_iterator position, Args&&... args);

Parameters

`position`	Specify hint for the position where the element can be inserted.
`args`	Arguments forwarded to construct the new element.

Return Value

Returns an iterator pointed to newly added element.

Time Complexity

Average case: Constant i.e, Θ(1).
Worst case: Linear i.e, Θ(n).

Example:

In the example below, the unordered_multiset::emplace_hint function is used to insert new element in the unordered_multiset called uMSet.

#include <iostream>
#include <unordered_set>
using namespace std;
 
int main (){
  unordered_multiset<int> uMSet{10, 20, 30, 40, 50};
  unordered_multiset<int>::iterator it; 

  it = uMSet.begin();
  uMSet.emplace_hint(it, 50);
  it = uMSet.emplace_hint(uMSet.end(), 60);
  
  cout<<"uMSet contains: ";
  for(it = uMSet.begin(); it != uMSet.end(); ++it)
    cout<<*it<<" ";

  return 0;
}

The output of the above code will be:

uMSet contains: 60 10 20 30 40 50 50

❮ C++ <unordered_set> Library