list::operator= in C++ STL

Lists are containers used in C++ to store data in a non contiguous fashion, Normally, Arrays and Vectors are contiguous in nature, therefore the insertion and deletion operations are costlier as compared to the insertion and deletion option in Lists.

list::operator=

This operator is used to assign new contents to the container by replacing the existing contents. It also modifies the size according to the new contents.

Time Complexity – Linear O(N)

Syntax :

listname1 = (listname2)
Parameters :
Another container of the same type.
Result :
Assign the contents of the container passed as 
parameter to the container written on left side of the operator.

Examples:

Input  :  mylist1 = 1, 2, 3
          mylist2 = 3, 2, 1, 4
          mylist1 = mylist2;
Output :  mylist1 = 3, 2, 1, 4

Input  :  mylist1 = 2, 6, 1, 5
          mylist2 = 3, 2
          mylist1 = mylist2;
Output :  mylist1 = 3, 2

Errors and Exceptions 1. If the containers are of different types, an error is thrown. 2. It has a basic no exception throw guarantee otherwise. 

CPP

// CPP program to illustrate
// Implementation of = operator
#include <iostream>
#include <list>
using namespace std;

int main()
{
 list<int> mylist1{ 1, 2, 3 };
 list<int> mylist2{ 3, 2, 1, 4 };
 mylist1 = mylist2;
 cout << "mylist1 = ";
 for (auto it = mylist1.begin();
   it != mylist1.end(); ++it)
  cout << ' ' << *it;
 return 0;
}

Output:

mylist1 = 3 2 1 4

Time Complexity: O(n)

Auxiliary Space: O(1)

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