Working with push_back()

This C++ program utilizes the Standard Template Library (STL) list to demonstrate basic operations with a linked list. Here's a breakdown of the code: 1. **Headers and Namespace**: - It includes the `iostream` header to handle input and output streams. - The `list` header is included for using the `list` container. - The `using namespace std;` line allows the use of standard library classes and functions without needing to prefix them with `std::`. 2. **Main Function**: - The `main()` function serves as the entry point of the program. - A `listint` named `values` is instantiated to store integers. - An iterator `it` is defined to traverse the list. 3. **Initial Size**: - The program outputs the initial size of the list, which is zero since no elements have been added yet. 4. **Adding Elements**: - It uses `push_back()` to add three integers (all with the value 5) to the end of the list. 5. **Inserting an Element**: - The iterator `it` is advanced to point to the second position in the list (after the first 5). - An integer 7 is inserted at this location using `t(it, 7)`. This places 7 in between the two 5s. 6. **Updated Size**: - It then outputs the updated size of the list, which should now be 4. 7. **Displaying the List**: - A loop iterates through the list, and each element is printed out on the same line, separated by tabs. In summary, this program initializes a list, adds elements, inserts an element at a specific position, and finally prints the size and contents of the list. The output will reflect the sequence of elements in the list after these operations, specifically: `5 7 5 5`.