C++ List Library - unique() Function

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Description

The C++ function std::list::unique() Removes all consecutive duplicate elements from the list. It uses operator== for comparison.

Declaration

Following is the declaration for std::list::unique() function form std::list header.

C++98

void unique();

Parameters

None

Return value

None

Exceptions

This member function never throws exception.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::list::unique() function.

#include <iostream>
#include <list>

using namespace std;

int main(void) {
   list <int> l = {1, 1, 2, 2, 3, 4, 5, 5};

   cout << "List elements before unique operation" << endl;

   for (auto it = l.begin(); it != l.end(); ++it)
      cout << *it << endl;

   l.unique();

   cout << "List elements after unique operation" << endl;

   for (auto it = l.begin(); it != l.end(); ++it)
      cout << *it << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

List elements before unique operation
1
1
2
2
3
4
5
5
List elements after unique operation
1
2
3
4
5