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std::binary_search

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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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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-Operationen
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Heap operations
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Minimum / Maximum Operationen
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Minimum/maximum operations
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Numerische Operationen
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Numeric operations
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C-Bibliothek
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C library
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definiert in Header <algorithm>
template< class ForwardIt, class T >
bool binary_search( ForwardIt first, ForwardIt last, const T& value );
 (1)
template< class ForwardIt, class T, class Compare >
bool binary_search( ForwardIt first, ForwardIt last, const T& value, Compare comp );
 (2)
Prüft, ob der sortierten Bereich [first, last) enthält ein Element gleich value. Die erste Version verwendet operator< um die Elemente zu vergleichen, verwendet die zweite Version des gegebenen Vergleichsfunktion comp .
Original:
Checks if the sorted range [first, last) contains an element equal to value. 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

true wenn ein Element gleich value gefunden wird, ansonsten false .
Original:
true if an element equal to value is found, false otherwise.
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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>
bool binary_search(ForwardIt first, ForwardIt last, const T& value)
{
    first = std::lower_bound(first, last, value);
    return (first != last && !(value < *first));
}
Second version 
template<class ForwardIt, class T, class Compare>
bool binary_search(ForwardIt first, ForwardIt last, const T& value, Compare comp)
{
    first = std::lower_bound(first, last, value);
    return (first != last && !(comp(value, *first));
}

[Bearbeiten] Beispiel

#include <iostream>
#include <algorithm>
#include <vector>
 
int main()
{
    std::vector<int> haystack {1, 3, 4, 5, 9};
    std::vector<int> needles {1, 2, 3};
 
    for (auto needle : needles) {
        std::cout << "Searching for " << needle << '\n';
        if (std::binary_search(haystack.begin(), haystack.end(), needle)) {
            std::cout << "Found " << needle << '\n';
        } else {
            std::cout << "no dice!\n";
        }
    }
}

Output: 

Searching for 1
Found 1
Searching for 2
no dice!
Searching for 3
Found 3

[Bearbeiten] Siehe auch
Bandbreite der Rendite von Elementen übereinstimmenden eine bestimmte Taste
Original:
returns range of elements matching a specific key
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