C++ Unordered_map Library - operator= Function

Description

The C++ function std::unordered_map::operator= assigns new contents to the unordered_map by replacing old ones and modifies size if necessary.

Declaration

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

C++11

unordered_map& operator=(const unordered_map& um);

Parameters

um − Another unordered_map object of same type.

Return value

Returns this pointer.

Time complexity

Linear i.e. O(n)

Example

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

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_map<char, int> um1 = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5}
            };

   unordered_map<char, int> um2;

   um2 = um1;

   cout << "Unordered map contains following elements: " << endl;

   for (auto it = um2.cbegin(); it != um2.cend(); ++it)
      cout << it->first << " = " << it->second << endl;

   return 0;
}

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

Unordered map contains following elements: 
e = 5
a = 1
b = 2
c = 3
d = 4