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std::equal_range

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Algorithm Bibliothek
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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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Sortierung Operationen (auf sortierten Bereiche)
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Sorting operations (on sorted ranges)
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Binary Suchaktionen (auf sortierten Bereiche)
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Binary search operations (on sorted ranges)
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binary_search
equal_range
Set-Operationen (auf sortierten Bereiche)
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Set operations (on sorted ranges)
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Heap operations
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C-Bibliothek
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C library
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Defined in header <algorithm>
template< class ForwardIt, class T >

std::pair<ForwardIt,ForwardIt>
    equal_range( ForwardIt first, ForwardIt last,

                 const T& value );
(1)
template< class ForwardIt, class T, class Compare >

std::pair<ForwardIt,ForwardIt>
    equal_range( ForwardIt first, ForwardIt last,

                 const T& value, Compare comp );
(2)

Gibt einen Bereich mit allen Elementen, die gleich value sind im Bereich [first, last), der bzgl. value aufgeteilt ist. Der Bereich wird durch zwei Iterationen, einer auf das erste Element, das nicht weniger' als value und ein anderer, der auf dem ersten Element' definiert ist größer als value. Mit lower_bound() .. - Der erste Iterator kann alternativ mit upper_bound(), die zweite erhalten werden.

Die erste Version verwendet operator< um die Elemente zu vergleichen, verwendet die zweite Version des gegebenen Vergleichsfunktion comp .
Original:
The first version uses operator< to compare the elements, the second version uses the given comparison function comp.
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Inhaltsverzeichnis

[Bearbeiten] Parameter

first, last -
das Spektrum der Elemente zu untersuchen
Original:
the range of elements to examine
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value -
Wert auf die Elemente zu vergleichen
Original:
value to compare the elements to
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comp - comparison function which returns ​true if the first argument is less than the second.

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

 bool cmp(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 type Type1 must be such that an object of type T can be implicitly converted to Type1. The type Type2 must be such that an object of type ForwardIt can be dereferenced and then implicitly converted to Type2. ​

Type requirements
-
ForwardIt must meet the requirements of ForwardIterator.

[Bearbeiten] Rückgabewert

std::pair enthaltend ein Paar von Iteratoren Definieren des gewünschten Bereichs, der erste auf das erste Element, das nicht weniger' als value und der zweite auf das erste Element' größer als value .
Original:
std::pair containing a pair of iterators defining the wanted range, the first pointing to the first element that is not less than value and the second pointing to the first element greater than value.
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Wenn keine Elemente' nicht weniger als value sind, wird last als erstes Element zurückgegeben. Ähnlich, wenn es keine Elemente' größer als value, last wird als zweites Element zurückgegeben
Original:
If there are no elements not less than value, last is returned as the first element. Similarly if there are no elements greater than value, last is returned as the second element
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[Bearbeiten] Komplexität

Logarithmisch im Abstand zwischen first und last
Original:
Logarithmic in the distance between first and last
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[Bearbeiten] Mögliche Implementierung

First version
template<class ForwardIt, class T 
std::pair<ForwardIt,ForwardIt> 
    equal_range(ForwardIt first, ForwardIt last,
                const T& value)
{
    return std::make_pair(std::lower_bound(first, last, value),
                          std::upper_bound(first, last, value));
}
Second version
template<class ForwardIt, class T, class Compare>
std::pair<ForwardIt,ForwardIt> 
    equal_range(ForwardIt first, ForwardIt last,
                const T& value, Compare comp);
{
    return std::make_pair(std::lower_bound(first, last, value, comp),
                          std::upper_bound(first, last, value, comp));
}

[Bearbeiten] Beispiel

#include <algorithm>
#include <vector>
#include <iostream>
 
struct S
{
    int number;
    char name;
 
    S ( int number, char name  )
        : number ( number ), name ( name )
    {}
 
    // only the number is relevant with this comparison
    bool operator< ( const S& s ) const
    {
        return number < s.number;
    }
};
 
 
int main()
{
    std::vector<S> vec = { {1,'A'}, {2,'B'}, {2,'C'}, {2,'D'}, {3,'F'}, {4,'G'} };
 
    S value ( 2, '?' );
 
    auto p = std::equal_range(vec.begin(),vec.end(),value);
 
    for ( auto i = p.first; i != p.second; ++i )
        std::cout << i->name << ' ';
}

Output:

B C D

[Bearbeiten] Siehe auch

liefert einen Iterator auf das erste Element nicht weniger als der angegebene Wert
Original:
returns an iterator to the first element not less than the given value
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(Funktions-Template) [edit]
liefert einen Iterator auf das erste Element mehr als ein bestimmter Wert
Original:
returns an iterator to the first element greater than a certain value
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(Funktions-Template) [edit]
bestimmt, ob ein Element vorhanden ist in einem gewissen Bereich
Original:
determines if an element exists in a certain range
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(Funktions-Template) [edit]