Replace all consecutive matching occurrences of a value in the range [ first ... last ) by a single instance of that value. Return an iterator positioned immediately after the last element of the new sequence. The size of the container is not altered. If n elements are removed, the last n elements of the sequence [ first ... last ) have undefined values. The first version uses operator== to match values, whereas the second version uses the binary function binary_pred .

Declaration


  
#include <algorithm>

template< class ForwardIterator >
ForwardIterator unique
  (
  ForwardIterator first,
  ForwardIterator last
  );

template< class ForwardIterator, class BinaryPredicate >
ForwardIterator unique
  (
  ForwardIterator first,
  ForwardIterator last,
  BinaryPredicate binary_pred
  );

Complexity

Time complexity is linear, as ( last - first ) operations are performed. Space complexity is constant.

Example <ospace/osstd/examples/unique1.cpp>


    #include <iostream>
#include <algorithm>

int numbers[ 8 ] = { 0, 1, 1, 2, 2, 2, 3, 4 };

int main()
  {
  unique( numbers, numbers + 8 );
  for ( int i = 0; i < 8; i ++ )
    cout << numbers[ i ] << ` `;
  cout << "\n";
  }

0 1 2 3 4 2 3 4

Example <ospace/osstd/examples/unique2.cpp>


    #include <iostream>
#include <string.h>
#include <algorithm>

char* labels[] = { "Q","Q","W","W","E","E","R","T","T","Y","Y" };

bool
str_equal( const char* a_, const char* b_ )
  {
  return ::strcmp( a_, b_ ) == 0 ? 1 : 0;
  }

int main()
  {
  const unsigned count = sizeof( labels ) / sizeof( labels[ 0 ] );
  ostream_iterator< char* > iter( cout );
  copy( labels, labels + count, iter );
  cout << "\n";

  unique( labels, labels + count, str_equal );
  copy( labels, labels + count, iter );
  cout << "\n";
  }

QQWWERRTTYY
QWERTYRTTYY

unique

Library

Declaration

Complexity

Example <ospace/osstd/examples/unique1.cpp>

Example <ospace/osstd/examples/unique2.cpp>