list::push_front() and list::push_back() in C++ STL

The C++ STL std::list is a doubly-linked list container that provides efficient insertion and deletion of elements at both the front and back of the list. You can use list::push_front() to insert an element at the beginning of the list, and list::push_back() to insert an element at the end of the list.

Here’s how you can use push_front() and push_back() with std::list:

#include <iostream>
#include <list>

int main() {
    std::list<int> myList;

    // Push elements to the front of the list using push_front()
    myList.push_front(1);
    myList.push_front(2);
    myList.push_front(3);

    // Push elements to the back of the list using push_back()
    myList.push_back(4);
    myList.push_back(5);
    myList.push_back(6);

    // Display the elements in the list
    for (const int& num : myList) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    return 0;
}

In this example:

• We create a std::list called myList.
• We use push_front() to insert elements at the beginning of the list (3, 2, and 1) and push_back() to insert elements at the end of the list (4, 5, and 6).
• Finally, we use a loop to iterate through the elements in the list and display them.

The output of this program will be:

3 2 1 4 5 6

Both push_front() and push_back() are efficient operations for std::list because it’s a doubly-linked list, and inserting elements at the beginning or end does not require shifting or moving other elements, unlike some other data structures like std::vector. This makes std::list a good choice when you need efficient insertion and removal of elements at both ends of the list.