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std::equal_range

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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
equal_range
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 >

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)
Devuelve una serie que contiene todos los elementos iguales a value en el [first, last) serie ordenada. El alcance se define por dos iteradores, una apuntando al primer elemento que es no a menos de value y otro apuntando al primer elemento mayores que value. El primer iterador puede ser obtenida con lower_bound() alternativamente, el segundo - con upper_bound() .
Original:
Returns a range containing all elements equal to value in the sorted range [first, last). The range is defined by two iterators, one pointing to the first element that is not less than value and another pointing to the first element greater than value. The first iterator may be alternatively obtained with lower_bound(), the second - with upper_bound().
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La primera versión utiliza operator< para comparar los elementos, la segunda versión utiliza la función de comparación dado comp .
Original:
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 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. ​

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

[editar] Valor de retorno

std::pair que contiene un par de los iteradores que definen el rango deseado, la primera apuntando al primer elemento que no es menor que value y el segundo elemento que apunta a la primera' mayor que 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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Si no hay elementos no a menos de value, last se devuelve como el primer elemento. Del mismo modo, si no hay elementos' mayor que value, last se devuelve como el segundo elemento
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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[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 
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));
}
Segunda versión
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));
}

[editar] Ejemplo

#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 << ' ';
}

Salida:

B C D

[editar] Ver también

devuelve un iterador al primer elemento no es menor que el valor dado
Original:
returns an iterator to the first element not less than the given value
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(plantilla de función) [editar]
devuelve un iterador al primer elemento' mayor que un cierto valor
Original:
returns an iterator to the first element greater than a certain value
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(plantilla de función) [editar]
determina si existe un elemento en un cierto rango
Original:
determines if an element exists in a certain range
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(plantilla de función) [editar]