C++ Deque::clear() Function

---

---

The C++ std::deque::clear() function is used to remove all elements from the deque, making its size zero. When this function is invoked, it destroys the objects contained in the deque and deallocates their memory, but the capacity of the deque remains unchanged.

Syntax

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

void clear() noexcept;

Parameters

It does not accepts any parameter.

Return value

This function does not return any thing.

Exceptions

This function never throws excpetion.

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 apply the clear() function on the integers deque.

#include <iostream>
#include <deque>
int main()
{
    std::deque<int> a {1,22,333,4444};
    std::cout << "Size before clear: " << a.size() << std::endl;
    a.clear();
    std::cout << "Size after clear: " << a.size() << std::endl;
    return 0;
}

Output

Output of the above code is as follows −

Size before clear: 4
Size after clear: 0

Example

Consider the another scenario, where we are going to use the clear() function on the string deque.

#include <iostream>
#include <deque>
#include <string>
int main()
{
    std::deque<std::string> a {"TP", "TutorialsPoint", "Tutorix"};
    std::cout << "Size before clear: " << a.size() << std::endl;
    a.clear();
    std::cout << "Size after clear: " << a.size() << std::endl;
    return 0;
}

Output

Following is the output of the above code −

Size before clear: 3
Size after clear: 0

Example

Following is the example, where we are going to apply the clear() function on the empty deque.

#include <iostream>
#include <deque>
int main()
{
    std::deque<int> a;
    a.clear();
    std::cout << "Size of the deque : " << a.size() << std::endl;
    return 0;
}

Output

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

Size of the deque : 0