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Apache C++ Standard Library Reference Guide

unique(), unique_copy()

Library:  Algorithms


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Summary

An algorithm that removes consecutive duplicates from a range of values and places the resulting unique values into the result

Synopsis

#include <algorithm>

namespace std {
  template<class ForwardIterator>
  ForwardIterator
  unique(ForwardIterator start, ForwardIterator finish);

  template<class ForwardIterator, class BinaryPredicate>
  ForwardIterator
  unique(ForwardIterator start, ForwardIterator finish,
         BinaryPredicate binary_pred);

  template<class InputIterator, class OutputIterator>
  OutputIterator
  unique_copy(InputIterator start, InputIterator finish,
              OutputIterator result);

  template <class InputIterator, class OutputIterator,
            class BinaryPredicate>
  OutputIterator
  unique_copy(InputIterator start, InputIterator finish,
              OutputIterator result,
              BinaryPredicate binary_pred);
}

Description

The unique() algorithm moves through a sequence and eliminates all but the first element from every consecutive group of equal elements. There are two versions of the algorithm -- one that tests for equality and a second that tests adjacent elements against a binary predicate. An element is unique if it does not meet the corresponding condition listed here:

*i == *(i - 1)

or

binary_pred(*i, *(i - 1)) == true.

If an element is unique, it is copied to the front of the sequence, overwriting the existing elements. Once all unique elements have been identified. The remainder of the sequence is left unchanged, and unique() returns the end of the resulting range.

The unique_copy() algorithm copies the first element from every consecutive group of equal elements to an output iterator. The unique_copy() algorithm also has two versions -- one that tests for equality and a second that tests adjacent elements against a binary predicate.

unique_copy() returns the end of the resulting range.

Complexity

For unique_copy(), exactly (finish - start) - 1 applications of the corresponding predicate are performed.

Example

Standards Conformance

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.2.8



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