In this we learn about std::list container. We also discuss the concept of iterators which is core to the C++ Standard Library.

1. Level up your coding skills with
the C++ Standard Template
Library (STL):
List
BY JOYJIT CHOUDHURY

2. List
 List is a sequence container that allows constant time
insertion and deletions anywhere in the container
 It allows iterations in both directions
 Fast random access is not supported
 List containers are implemented as Doubly Linked List
 Defined in the header <list>
 Belongs to the namespace std

3. Construction of a list

4. Accessing the elements
 Member functions front() and back(), returns a
reference to the first and last element of the list,
respectively
front() back()

5. Accessing the elements
 front() and back() return a reference, so not only can
you view the first and last element, you can also modify
them
list<int> mylist

6. Insert elements
 Member functions push_front() and push_back(), inserts an element
to the beginning and the end of the list, respectively

7. Delete elements
 Member functions pop_front() and pop_back(), removes the first
and the last element of the list, respectively

8. Size of the list
 Member function size() returns the number of elements in the list
 Time Complexity : O(n)

9. Is the list empty?
 Member function empty() returns true if the list is empty (i.e. list size is 0),
else returns false
 Time Complexity : O(1)
 It’s a preferred way to check
whether a list is empty,
instead of checking whether
the size of the list is 0, since
this takes constant time

10. So, how do you Traverse a list?
 The thing about containers is, you hardly know anything about it’s internal
mechanisms
 All the internal details regarding :
 How the memory is allocated
 Where and how the data elements are stored
 How the insertion, access and removal of individual elements take place
It’s all kept hidden from the user.
 So, what if you had to access the individual elements, maybe even modify
them?
 For that purpose, containers have what is known as Iterators

11. What are Iterators?
 An iterator is an object, pointing to some element in a range of
elements (usually, a container), which has the ability to iterate through
the elements in that range through a set of operators
(increment (++) operator, dereference (*) operator, etc)
 You can think of them as an abstraction of pointers
 What that means is, they are like pointers in certain ways, but not
exactly

12. Iterators
 The best way to understand iterators, would be through an example
list<int> myList
myList.begin()

13. Iterators
list<int> myList
myList.begin() myList.end()

14. Insert elements anywhere in the list
 Member function insert(), inserts new elements before the element at
the specified position. The position is specified by passing an iterator as a
parameter.

15. Delete elements from anywhere
 Member function erase(), removes from the list, either a single element from
the specified position, or all the elements in the specified range [first, last).

16.  That’s not all. There are many other functions
and techniques that could come in handy.
Read about them on cplusplus.com or
cppreference.com or somewhere else. Just
google it!