C++ Unordered_multimap Library - swap() Function

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Description

The C++ function std::unordered_multimap::swap() exchanges the content of first unordered_multimap with another.

Declaration

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

C++11

template <class Key, class T, class Hash, class Pred, class Alloc>
void swap(unordered_multimap<Key,T,Hash,Pred,Alloc>& first,
          unordered_multimap<Key,T,Hash,Pred,Alloc>& second);

Parameters

• first − First unordered_multimap object.

• second − Second unordered_multimap object.

Return value

None

Time complexity

Constant i.e. O(1)

Example

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

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_multimap<char, int> umm1 = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5}
            };
   unordered_multimap<char, int> umm2;

   swap(umm1, umm2);

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

   for (auto it = umm2.begin(); it != umm2.end(); ++it)
      cout << it->first << " = " << it->second << endl;

   return 0;
}

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

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