C++ STL Multiset Operator!=() Function

Introduction

Multiset is a container in C++ STL (Standard Template Library) that stores elements in a sorted order. It is implemented using a balanced binary tree, specifically the red-black tree. The multiset container is similar to the set container, with the difference that the multiset container allows duplicate elements.

The operator!=() function is a member function of the multiset container that is used to compare two multiset containers. It returns true if the two multiset containers are not equal and false otherwise.

Syntax

The syntax for the operator!=() function is as follows:

bool operator!=(const multiset& other) const;

Here, other is the multiset container to be compared with. The function returns a boolean value. If the multiset containers are not equal, the function returns true. If they are equal, the function returns false.

Example

Consider the following code snippet:

#include <iostream>
#include <set>

int main()
{
    std::multiset<int> set1{1, 2, 3};
    std::multiset<int> set2{3, 2, 1};
    std::multiset<int> set3{1, 2, 3, 4};
    
    std::cout << std::boolalpha;
    std::cout << (set1 != set2) << std::endl; // Outputs false
    std::cout << (set1 != set3) << std::endl; // Outputs true
    
    return 0;
}

In this example, we create three multiset containers set1, set2, and set3. We then use the operator!=() function to compare these multiset containers. The output of the program is as follows:

false
true

This is because set1 and set2 have the same elements, but in a different order, whereas set1 and set3 have different number of elements.

Conclusion

The operator!=() function is a useful member function of the multiset container that allows us to compare two multiset containers. It returns true if the two containers are not equal and false otherwise.