C++ Map Library - operator= Function

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Description

The C++ function std::map::operator= move the contents of one map into another and modifies size if necessary.

Declaration

Following is the declaration for std::map::operator= function form std::map header.

C++11

map& operator= (map&& x);

Parameters

x − Another map object of same type

Return value

Returns this pointer

Exceptions

This member function doesn't throw exception.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::map::operator= function.

#include <iostream>
#include <map>

using namespace std;

int main(void) {
   /* Initializer_list constructor */
   map<char, int> m1 = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5},
            };

   map<char, int> m2 = move(m1);

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

   for (auto it = m2.begin(); it != m2.end(); ++it)
      cout << it->first << " = " << it->second << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Map contains following elements
a = 1
b = 2
c = 3
d = 4
e = 5