Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.
NAME
unique, unique_copy
- Removes consecutive duplicates from a range of values and
places the resulting unique values into the result.
SYNOPSIS
#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);
template <class InputIterator, class OutputIterator>
OutputIterator
unique_copy (InputIterator first, InputIterator last,
OutputIterator result);
template <class InputIterator, class OutputIterator,
class BinaryPredicate>
OutputIterator
unique_copy (InputIterator first, InputIterator last,
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 result-
ing range.
The unique_copy algorithm copies the first element from
every consecutive group of equal elements to an OutputItera-
tor. 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, it is exactly (last - first) - 1 applica-
tions of the corresponding predicate are performed.
EXAMPLE
//
// unique.cpp
//
#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;
int main()
{
//Initialize two vectors
int a1[20] = {4, 5, 5, 9, -1, -1, -1, 3, 7, 5,
5, 5, 6, 7, 7, 7, 4, 2, 1, 1};
vector<int> v(a1+0, a1+20), result;
//Create an insert_iterator for results
insert_iterator<vector<int> > ins(result, result.begin());
//Demonstrate includes
cout << "The vector: " << endl << " ";
copy(v.begin(),v.end(),
ostream_iterator<int,char>(cout," "));
//Find the unique elements
unique_copy(v.begin(), v.end(), ins);
//Display the results
cout << endl << endl
<< "Has the following unique elements:"
<< endl << " ";
copy(result.begin(),result.end(),
ostream_iterator<int,char>(cout," "));
return 0;
}
Program Output
The vector:
4 5 5 9 -1 -1 -1 3 7 5 5 5 6 7 7 7 4 2 1 1
Has the following unique elements:
4 5 9 -1 3 7 5 6 7 4 2 1
WARNINGS
If your compiler does not support default template parame-
ters, then you always need to supply the Allocator template
argument. For instance, you need to write:
vector<int, allocator<int> >
instead of:
vector<int>
If your compiler does not support namespaces, then you do
not need the using declaration for std.