C++ Map Library - swap() Function


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Description

The C++ function std::map::swap() exchanges the content of map with contents of map x.

Declaration

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

C++98

template <class Key, class T, class Compare, class Alloc>
void swap (map<Key,T,Compare,Alloc>& first, 
   map<Key,T,Compare,Alloc>& second);

Parameters

  • first − First map object.

  • second − Second map object of same type.

Return value

None

Exceptions

This function doesn't throw exception.

Time complexity

Constant i.e. O(1)

Example

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

#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;

   swap(m1, m2);

   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
map.htm
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