C++ multimap :: operator!=() Function

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The C++ std::multimap::operator!=() is used to check whether the two multimaps are not equal. It compares the elements and their counts in both multimaps. If they differ, It returns true orelse it return false. This function ensures that the two multimaps are not identical in terms of their key-value pairs and occurences.

Syntax

Following is the syntax for std::multimap::operator!=() function.

bool operator!=( const std::multimap<Key, T, Compare, Alloc>& lhs,
                 const std::multimap<Key, T, Compare, Alloc>& rhs );

Parameters

• lhs − It indicates the first multimap object.
• rhs − It indicates the second multimap object

Return value

This function returns true if both mutlimap are not equal otherwise false.

Exceptions

This function doesn't throw exception.

Time complexity

The time complexity of this function is Linear i.e. O(n)

Example

Let's look at the following example, where we are going to demonstrate the usage of operator!=() function.

#include <iostream>
#include <map>
int main()
{
    std::multimap<int, std::string> a;
    std::multimap<int, std::string> b;
    a.insert({1, "Hi"});
    b.insert({1, "Hi"});
    if (a != b) {
        std::cout << "Multimaps are not equal" << std::endl;
    } else {
        std::cout << "Multimaps are equal" << std::endl;
    }
    return 0;
}

Output

Output of the above code is as follows −

Multimaps are equal

Example

Consider the following example, where we are going to have the same number of elements, with different keys.

#include <iostream>
#include <map>
int main()
{
    std::multimap<int, std::string> a;
    std::multimap<int, std::string> b;
    a.insert({1, "Hi"});
    b.insert({3, "Hi"});
    if (a != b) {
        std::cout << "Multimaps are not equal" << std::endl;
    } else {
        std::cout << "Multimaps are equal" << std::endl;
    }
    return 0;
}

Output

Following is the output of the above code −

Multimaps are not equal

Example

In the following example, we are going to compare the multimap having different elements and observing the output.

#include <iostream>
#include <map>
int main()
{
    std::multimap<int, std::string> a;
    std::multimap<int, std::string> b;
    a.insert({1, "Hi"});
    b.insert({1, "Hello"});
    if (a != b) {
        std::cout << "Multimaps are not equal." << std::endl;
    } else {
        std::cout << "Multimaps are equal." << std::endl;
    }
    return 0;
}

Output

If we run the above code it will generate the following output −

Multimaps are not equal.