C++ multiset - operator=() Function

The C++ multiset::operator= function is used to assign new content to the container by replacing the current content.

Syntax

C++98
C++11

//copies all elements of x into the container
multiset& operator= (const multiset& x);

//copy version - copies all elements
//of x into the container
multiset& operator= (const multiset& x);

//move version - moves elements of x
//into the container
multiset& operator= (multiset&& x);

//initializer list version - copies all 
//elements of il into the container
multiset& operator= (initializer_list<value_type> il);

Parameters

`x`	Specify a multiset object of same type.
`il`	Specify an initializer_list object.

Return Value

Returns *this.

Time Complexity

Linear i.e, Θ(n) for copy version and move version.
Up to logarithmic i.e, Θ(nlog(n)). Linear i.e, Θ(n) if il is already sorted.

Example: using copy version

In the example below, the multiset::operator= function is used to assign new values to the given multiset.

#include <iostream>
#include <set>
using namespace std;
 
int main (){
  multiset<int> mset1{15, 5, 23, 78, 41};
  multiset<int>::iterator it;

  //copying all content of mset1 into mset2
  multiset<int> mset2;
  mset2 = mset1;

  cout<<"The mset1 contains:";
  for(it = mset1.begin(); it != mset1.end(); ++it)
    cout<<" "<<*it;

  cout<<"\nThe mset2 contains:";
  for(it = mset2.begin(); it != mset2.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

The mset1 contains: 5 15 23 41 78
The mset2 contains: 5 15 23 41 78

Example: using move version

Using the move version of operator=, the content of one multiset can be moved to another multiset. Consider the following example:

#include <iostream>
#include <set>
using namespace std;
 
int main (){
  multiset<int> mset1{15, 5, 23, 78, 41};
  multiset<int>::iterator it;

  cout<<"The mset1 contains:";
  for(it = mset1.begin(); it != mset1.end(); ++it)
    cout<<" "<<*it;

  //moving all content of mset1 into mset2
  multiset<int> mset2;
  mset2 = move(mset1);

  cout<<"\nThe mset1 contains:";
  for(it = mset1.begin(); it != mset1.end(); ++it)
    cout<<" "<<*it;

  cout<<"\nThe mset2 contains:";
  for(it = mset2.begin(); it != mset2.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

The mset1 contains: 5 15 23 41 78
The mset1 contains:
The mset2 contains: 5 15 23 41 78

Example: using initializer list version

The initializer list can also be used to assign values into a multiset container. Consider the example below:

#include <iostream>
#include <set>
using namespace std;
 
int main (){
  //creating empty multiset
  multiset<int> mset;
  multiset<int>::iterator it;

  //creating initializer list
  initializer_list<int> ilist = {15, 5, 23, 78, 41};

  //assigning values of mset using ilist
  mset = ilist;

  cout<<"mset contains:";
  for(it = mset.begin(); it != mset.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

mset contains: 5 15 23 41 78

❮ C++ <set> Library