forward_list::unique() in C++

Forward lists are sequence structures that allow constant-time insert and erase processes anywhere in the sequence. Forward lists are implemented as singly linked lists. The ordering is maintained by associating each element with a link to the next element in the sequence.

forward_list::unique() is a function in the C++ standard library that is used to eliminate all duplicate entries from a forward list. It should be noted that an element is only deleted from the forward_list container if it compares to the element immediately before it. As a result, this method is especially helpful for sorted lists.

Syntax:

It has the following syntax:

Syntax for the binary predicate:

This function takes a single parameter, it is a binary predicate that returns true if the items should be considered as equal.

Approach

The fundamental drawback of utilizing list and forward_list over other sequence containers is that they do not provide direct access to any element by its location, such as using the operator []. To access any of the elements in a forward_list, iteration must be performed from a known point (such as the starting point or end of the list) to the element's position, requiring linear time.

Example:

Let's take an example to illustrate the use of forward_list_unique() function in C++.

Output:

The elements of the list before the unique operation: 1 1 4 4 4 2 2 2 2 5 5 5 5 5 
Elements after the unique operation is: 1 4 2 5