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std::binary_search

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< cpp‎ | algorithm
 
 
Biblioteca de algoritmos
Políticas de ejecución (C++17)
Operaciones no modificadoras de secuencia
(C++11)(C++11)(C++11)
(C++17)
Operaciones modificadoras de secuencia
Operaciones en almacenamiento no inicializado
Operaciones de partición
Operaciones de ordenación
(C++11)
Operaciones de búsqueda binaria
binary_search
Operaciones de set (en rangos ordenados)
Operaciones de pila
(C++11)
Operaciones minimo/maximo
(C++11)
(C++17)
Permutaciones
Operaciones numéricas
Bibliotecas C
 
Definido en la cabecera <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)
Comprueba si el rango [first, last) ordenados contiene un elemento igual a value. La primera versión utiliza operator< para comparar los elementos, la segunda versión utiliza la función de comparación dado 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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Contenido

[editar] Parámetros

first, last -
la gama de elementos a examinar
Original:
the range of elements to examine
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value -
valor para comparar los elementos a
Original:
value to compare the elements to
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comp - comparison function object (i.e. an object that satisfies the requirements of Compare) 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);

While the signature does not need to have const &, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1 & is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy (desde C++11)).
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. ​

Requerimientos de tipo
-
ForwardIt debe reunir los requerimientos de ForwardIterator.

[editar] Valor de retorno

true si un elemento igual a value se encuentra, por lo demás false .
Original:
true if an element equal to value is found, false otherwise.
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[editar] Complejidad

Logarítmica en la distancia entre first y last
Original:
Logarithmic in the distance between first and last
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[editar] Posible implementación

Primera versión
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));
}
Segunda versión
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));
}

[editar] Ejemplo

#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";
        }
    }
}

Salida:

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

[editar] Ver también

El rendimiento es de los elementos que coinciden con una clave específica
Original:
returns range of elements matching a specific key
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(plantilla de función) [editar]