std::binary_search - cppreference.com

std::binary_search

Da cppreference.com.

<metanoindex/>

 
C++
 
Algoritmo libreria
Funzioni
Original:
Functions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Non modifica le operazioni di sequenza
Original:
Non-modifying sequence operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Modifica delle operazioni di sequenza
Original:
Modifying sequence operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Partizionamento operazioni
Original:
Partitioning operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Ordinamento delle operazioni (su intervalli ordinati)
Original:
Sorting operations (on sorted ranges)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Binarie (le operazioni di ricerca sui campi ordinati)
Original:
Binary search operations (on sorted ranges)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Impostare le operazioni (su intervalli ordinati)
Original:
Set operations (on sorted ranges)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Heap operazioni
Original:
Heap operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Minimo / massimo le operazioni
Original:
Minimum/maximum operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Operazioni numeriche
Original:
Numeric operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Libreria C
Original:
C library
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
 
<tbody> </tbody>
Elemento definito nell'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)
Controlla se il [first, last) gamma ordinato contiene un elemento uguale a value. La prima versione utilizza operator< di confrontare gli elementi, la seconda versione utilizza la funzione di confronto dato 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.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Parametri

first, last -
la gamma di elementi da esaminare
Original:
the range of elements to examine
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
value -
valore per confrontare gli elementi
Original:
value to compare the elements to
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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.

Valore di ritorno

true se un elemento uguale a value si trova, false altrimenti.
Original:
true if an element equal to value is found, false otherwise.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Complessità

Logaritmica della distanza tra first e last
Original:
Logarithmic in the distance between first and last
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Possibile implementazione

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));
}

Esempio

#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

Vedi anche