C++ Unordered_map Library - operator!= Function

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Description

The C++ function std::unordered_map::operator!= tests whether two unordered_maps are equal or not.

Declaration

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

C++11

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

Parameters

• first − First unordered_map object.

• second − Second unordered_map object.

Return value

Returns true if both unordered_map are not equal otherwise false.

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> um1;
   unordered_map<char, int> um2;

   um1.emplace('a', 1);

   if (um1 != um2)
      cout << "Both unordered_maps not are equal" << endl;

   um1 = um2;

   if (!(um1 != um2))
      cout << "Both unordered_maps are equal" << endl;

   return 0;
}

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

Both unordered_maps not are equal
Both unordered_maps are equal