C++ Deque::operator==() Function

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The C++ std::deque::operator==() function is used to compare the two deque containers. It checks if both the deque objects are of the same size and contains the same elements in the same order. If both the conditions are met, it returns true otherwise it returns false.

Syntax

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

bool operator== (const deque<T,Alloc>& lhs, const deque<T,Alloc>& rhs);

Parameters

• lhs, rhs − It indicates the deque containers.

Return value

This function returns true if the condition holds otherwise false.

Exceptions

This function never throws exception.

Time complexity

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

Example

In the following example, we are going to consider the basic usage of operator==() function.

#include <iostream>
#include <deque>
int main()
{
    std::deque<int> a = {11,22,333};
    std::deque<int> b = {11,22,333};
    if (a == b) {
        std::cout << "Deques are equal." << std::endl;
    } else {
        std::cout << "Deques are not equal." << std::endl;
    }
    return 0;
}

Output

Following is the output of the above code −

Deques are equal.

Example

Consider the following example, where we are going to compare the deques of different sizes.

#include <iostream>
#include <deque>
int main()
{
    std::deque<int> a = {1,22,333};
    std::deque<int> b = {1,22};
    if (a == b) {
        std::cout << "Deques are equal." << std::endl;
    } else {
        std::cout << "Deques are not equal." << std::endl;
    }
    return 0;
}

Output

Output of the above code is as follows −

Deques are not equal.

Example

In the following example, we are going to compare the deque of empty queue and observing the output.

#include <iostream>
#include <deque>
int main()
{
    std::deque<char> a;
    std::deque<char> b;
    if (a == b) {
        std::cout << "Deques are equal." << std::endl;
    } else {
        std::cout << "Deques are not equal." << std::endl;
    }
    return 0;
}

Output

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

Deques are equal.