C++ Unordered_multimap Library - operator==() Function

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Description

The C++ function std::unordered_multimap::operator==() tests whether two unordered_multimaps are equal or not.

Declaration

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

C++11

template <class Key, class T, class Hash, class Pred, class Alloc>
bool operator==(const unordered_multimap<Key,T,Hash,Pred,Alloc>& first,
                const unordered_multimap<Key,T,Hash,Pred,Alloc>& second);

Parameters

• first − First unordered_multimap object.

• second − Second unordered_multimap object.

Return value

Returns true if both unordered_multimaps are equal otherwise false.

Time complexity

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

Quadratic i.e. O(n²) in worst case.

Example

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_multimap<char, int> umm1;
   unordered_multimap<char, int> umm2;

   if (umm1 == umm2)
      cout << "Both unordered_multimaps are equal." << endl;

   umm1.emplace('a', 1);

   if (!(umm1 == umm2))
      cout << "Both unordered_multimaps are not equal." << endl;

   return 0;
}

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

Both unordered_multimaps are equal.
Both unordered_multimaps are not equal.