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std::unique_copy

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C++
 
Algorithm Bibliothek
Funktionen
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Functions
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Nicht-modifizierende Sequenz Operationen
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Non-modifying sequence operations
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Modifizierende Sequenz Operationen
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Modifying sequence operations
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Partitionierungsoperationen
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Partitioning operations
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Sorting operations (on sorted ranges)
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Binary search operations (on sorted ranges)
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Set operations (on sorted ranges)
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Heap operations
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Minimum/maximum operations
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definiert in Header <algorithm>
template< class InputIt, class OutputIt >

ForwardIt unique_copy( InputIt first, InputIt last,

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

ForwardIt unique_copy( InputIt first, InputIt last,

                       OutputIt d_first, BinaryPredicate p );
 (2)
Kopiert die Elemente aus dem Bereich [first, last), in einen anderen Bereich beginnend bei d_first derart, dass es keine aufeinanderfolgenden gleichen Elemente. Nur das erste Element einer jeden Gruppe von gleichen Elementen kopiert wird. Die erste Version verwendet operator== um die Elemente zu vergleichen, verwendet die zweite Version des gegebenen binären Prädikats p .
Original:
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.
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Inhaltsverzeichnis

[Bearbeiten] Parameter

first, last -
der Bereich der Elemente zu verarbeiten
Original:
the range of elements to process
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d_first -
der Beginn des Zielbereichs
Original:
the beginning of the destination range
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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 ForwardIt 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.
-
The type of dereferenced InputIt must meet the requirements of CopyConstructible. if neither InputIt nor OutputIt satisfies ForwardIterator

[Bearbeiten] Rückgabewert

Output Iterator auf das Element nach dem letzten schriftlichen Element
Original:
Output iterator to the element past the last written element
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[Bearbeiten] Mögliche Implementierung

First version 
template<class ForwardIt, class OutputIt>
ForwardIt unique_copy(ForwardIt first, ForwardIt last,
                      OutputIt d_first)
{
 
    if (first == last)
        return d_first;
 
    *d_first = *first;
     while (++first != last) {
        if (!(*d_first == *first)) {
            *(++d_first) = *first;
        }
    }
    return ++d_first;
}
Second version 
template<class ForwardIt, class OutputIt, class BinaryPredicate>
ForwardIt unique_copy(ForwardIt first, ForwardIt last,
                            OutputIt d_first, BinaryPredicate p)
{
 
    if (first == last)
        return d_first;
 
    *d_first = *first;
    while (++first != last) {
        if (!p(*result, *first)) {
            *(++d_first) = *first;
        }
    }
    return ++d_first;
}

[Bearbeiten] Beispiel

Das folgende Programm trimmt alle mehrere aufeinander folgende Leerzeichen in einer const string und gibt das Ergebnis
Original:
The following program trims all multiple consecutive spaces in a const string and prints the result
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#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!

[Bearbeiten] Komplexität

linear im Abstand first und last
Original:
linear in the distance between first and last
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[Bearbeiten] Siehe auch
findet zwei identischen (oder eine andere Beziehung) Elemente einander benachbart
Original:
finds two identical (or some other relationship) items adjacent to each other
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(Funktions-Template) [edit]
removes consecutive duplicate elements in a range
(Funktions-Template) [edit]
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/algorithm/unique_copy&oldid=26127“