list::unique

Removes adjacent duplicate elements or adjacent elements that satisfy some other binary predicate from a list.

void unique( );
template<class BinaryPredicate>
   void unique(
      BinaryPredicate _Pred
   );

Parameters

  • _Pred
    The binary predicate used to compare successive elements.

Remarks

This function assumes that the list is sorted, so that all duplicate elements are adjacent. Duplicates that are not adjacent will not be deleted.

The first member function removes every element that compares equal to its preceding element.

The second member function removes every element that satisfies the predicate function _Pred when compared with its preceding element.

Example

// list_unique.cpp
// compile with: /EHsc
#include <list>
#include <iostream>

int main( )
{
   using namespace std;
   list <int> c1;
   list <int>::iterator c1_Iter, c2_Iter,c3_Iter;
   not_equal_to<int> mypred;
   
   c1.push_back( -10 );
   c1.push_back( 10 );
   c1.push_back( 10 );
   c1.push_back( 20 );
   c1.push_back( 20 );
   c1.push_back( -10 );

   cout << "The initial list is c1 =";
   for ( c1_Iter = c1.begin( ); c1_Iter != c1.end( ); c1_Iter++ )
      cout << " " << *c1_Iter;
   cout << endl;
   
   list <int> c2 = c1;
   c2.unique( );
   cout << "After removing successive duplicate elements, c2 =";
   for ( c2_Iter = c2.begin( ); c2_Iter != c2.end( ); c2_Iter++ )
      cout << " " << *c2_Iter;
   cout << endl;

   list <int> c3 = c2;
   c3.unique( mypred );
   cout << "After removing successive unequal elements, c3 =";
   for ( c3_Iter = c3.begin( ); c3_Iter != c3.end( ); c3_Iter++ )
      cout << " " << *c3_Iter;
   cout << endl;
}

The initial list is c1 = -10 10 10 20 20 -10
After removing successive duplicate elements, c2 = -10 10 20 -10
After removing successive unequal elements, c3 = -10 -10

Requirements

Header: <list>

Namespace: std

See Also

Concepts

list Class

list Class Members

Standard Template Library