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std::set_intersection

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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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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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Set-Operationen (auf sortierten Bereiche)
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Set operations (on sorted ranges)
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Heap-Operationen
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Heap operations
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Minimum/maximum operations
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Numeric operations
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C-Bibliothek
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C library
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Defined in header <algorithm>
template< class InputIt1, class InputIt2, class OutputIt >

OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
                           InputIt2 first2, InputIt2 last2,

                           OutputIt d_first );
(1)
template< class InputIt1, class InputIt2,

          class OutputIt, class Compare >
OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
                           InputIt2 first2, InputIt2 last2,

                           OutputIt d_first, Compare comp );
(2)
Konstruiert eine sortierte Bereich ab ca. d_first bestehend aus Elementen, die in beiden sortierten Bereiche gefunden werden [first1, last1) und [first2, last2). Die erste Version rechnet sowohl Eingangsbereiche mit operator< sortiert werden, rechnet die zweite Version sie mit dem angegebenen Vergleichsfunktion comp sortiert werden. Wenn ein Element ist m mal gefunden [first1, last1) und n Mal in [first2, last2) die ersten std::min(m, n) Elemente aus dem ersten Bereich, um den Zielbereich kopiert werden. Die Reihenfolge der äquivalente Elemente erhalten bleibt. Die daraus resultierende Bereich kann nicht mit einem der Eingangsbereiche überschneiden .
Original:
Constructs a sorted range beginning at d_first consisting of elements that are found in both sorted ranges [first1, last1) and [first2, last2). The first version expects both input ranges to be sorted with operator<, the second version expects them to be sorted with the given comparison function comp. If some element is found m times in [first1, last1) and n times in [first2, last2), the first std::min(m, n) elements will be copied from the first range to the destination range. The order of equivalent elements is preserved. The resulting range cannot overlap with either of the input ranges.
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Inhaltsverzeichnis

[Bearbeiten] Parameter

first1, last1 -
die erste Reihe von Elementen zu prüfen
Original:
the first range of elements to examine
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first2, last2 -
der zweite Bereich von Elementen zu prüfen
Original:
the second range of elements to examine
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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 types Type1 and Type2 must be such that objects of types InputIt1 and InputIt2 can be dereferenced and then implicitly converted to Type1 and Type2 respectively. ​

Type requirements
-
InputIt1 must meet the requirements of InputIterator.
-
InputIt2 must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

[Bearbeiten] Rückgabewert

Iterator über das Ende der konstruiert Bereich .
Original:
Iterator past the end of the constructed range.
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[Bearbeiten] Komplexität

Allenfalls 2·(N1+N2-1) Vergleiche, wo N1 = std::distance(first1, last1) und N2 = std::distance(first2, last2) .
Original:
At most 2·(N1+N2-1) comparisons, where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).
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[Bearbeiten] Mögliche Implementierung

First version
template<class InputIt1, class InputIt2, class OutputIt>
OutputIt set_intersection(InputIt1 first1, InputIt1 last1,
                          InputIt2 first2, InputIt2 last2,
                          OutputIt d_first)
{
    while (first1 != last1 && first2 != last2) {
        if (*first1 < *first2) {
            ++first1;
        } else  {
            if (!(*first2 < *first1)) {
                *d_first++ = *first1++;
            }
            ++first2;
        }
    }
    return d_first;
}
Second version
template<class InputIt1, class InputIt2,
         class OutputIt, class Compare>
OutputIt set_intersection(InputIt1 first1, InputIt1 last1,
                          InputIt2 first2, InputIt2 last2,
                          OutputIt d_first, Compare comp)
{
    while (first1 != last1 && first2 != last2) {
        if (comp(*first1, *first2)) {
            ++first1;
        } else {
            if (!comp(*first2, *first1)) {
                *d_first++ = *first1++;
            }
            ++first2;
        }
    }
    return d_first;
}


[Bearbeiten] Beispiel

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
int main()
{
    std::vector<int> v1{1,2,3,4,5,6,7,8};
    std::vector<int> v2{        5,  7,  9,10};
    std::sort(v1.begin(), v1.end());
    std::sort(v2.begin(), v2.end());
 
    std::vector<int> v_intersection;
 
    std::set_intersection(v1.begin(), v1.end(),
                          v2.begin(), v2.end(),
                          std::back_inserter(v_intersection));
    for(int n : v_intersection)
        std::cout << n << ' ';
}

Output:

5 7

[Bearbeiten] Siehe auch

computes the union of two sets
(Funktions-Template) [edit]