C++ Unordered_map Library - operator= Function

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Description

The C++ function std::unordered_map::operator= copy elements from initializer list to unordered_map.

Declaration

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

C++11

unordered_map& operator=(intitializer_list<value_type> il);

Parameters

il − Initialize list.

Return value

Returns this pointer

Time complexity

Linear i.e. O(n) in average case.

Quadratic i.e. O(n²) in worst case.

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> um;

   um = {
         {'a', 1},
         {'b', 2},
         {'c', 3},
         {'d', 4},
         {'e', 5}
      };

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

   for (auto it = um.cbegin(); it != um.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
d = 4
c = 3
b = 2
a = 1