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std::unique_copy

From cppreference.com
< cpp‎ | algorithm
 
 
 
Defined in header <algorithm>
template< class InputIt, class OutputIt >

OutputIt unique_copy( InputIt first, InputIt last,

                      OutputIt d_first );
(1)
template< class InputIt, class OutputIt, class BinaryPredicate >

OutputIt unique_copy( InputIt first, InputIt last,

                      OutputIt d_first, BinaryPredicate p );
(2)

Copies the elements from the range [first, last), to another range beginning at d_first in such a way that there are no consecutive equal elements. Only the first element of each group of equal elements is copied. The first version uses operator== to compare the elements, the second version uses the given binary predicate p.

Contents

[edit] Parameters

first, last - the range of elements to process
d_first - the beginning of the destination range
p - binary predicate which returns ​true if the elements should be treated as equal.

The signature of the predicate function should be equivalent to the following:

 bool pred(const Type1 &a, const Type2 &b);

The signature does not need to have const &, but the function must not modify the objects passed to it.
The types Type1 and Type2 must be such that an object of type InputIt can be dereferenced and then implicitly converted to both of them.

Type requirements
-
InputIt must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.
-
The type of dereferenced InputIt must meet the requirements of CopyAssignable. if InputIt does not satisfy ForwardIterator
-
The type of dereferenced InputIt must meet the requirements of CopyConstructible. if neither InputIt nor OutputIt satisfies ForwardIterator, or if InputIt does not satisfy ForwardIterator and the value type of InputIt differs from that of OutputIt

[edit] Return value

Output iterator to the element past the last written element

[edit] Complexity

For nonempty ranges, exactly std::distance(first, last) - 1 applications of the corresponding comparator.

[edit] Notes

If InputIt satisfies ForwardIterator, this function rereads the input in order to detect duplicates.

Otherwise, if OutputIt satisfies ForwardIterator, and the value type of InputIt is the same as that of OutputIt, this function compare *d_first to *first.

Otherwise, this function compares *first to a local element copy.

[edit] Example

#include <string>
#include <iostream>
#include <algorithm>
#include <iterator>
 
int main()
{
    std::string s1 = "The      string    with many       spaces!";
    std::cout << "before: " << s1 << '\n';
 
    std::string s2;
    std::unique_copy(s1.begin(), s1.end(), std::back_inserter(s2),
                     [](char c1, char c2){ return c1 == ' ' && c2 == ' '; });
 
    std::cout << "after:  " << s2 << '\n';
}

Output:

before: The      string    with many       spaces!
after:  The string with many spaces!

[edit] See also

finds the first two adjacent items that are equal (or satisfy a given predicate)
(function template) [edit]
removes consecutive duplicate elements in a range
(function template) [edit]