C++ Map Library - map() Function

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Description

The C++ constructor std::map::map() constructs a map with the contents of other using move semantics.

Declaration

Following is the declaration for std::map::map() constructor form std::map header.

C++11

map (map&& other);
map (map&& other, const allocator_type& alloc);

Parameters

• other - Another map object of same type.

• alloc - The allocator object.

Return value

Constructor never returns value.

Exceptions

This member function never throws exception.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::map::map() constructor.

#include <iostream>
#include <map>

using namespace std;

int main(void)
{
   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