unique(3C++) - unique(3C++)
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 ele‐
ment 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 consecu‐
tive group of equal elements to an OutputIterator. The unique_copy
algorithm also has two versions-one that tests for equality and a sec‐
ond 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 applications 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 OutputThe 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 parameters, 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.
Rogue Wave Software 02 Apr 1998 unique(3C++)
