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std::unique

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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
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 >
ForwardIt unique( ForwardIt first, ForwardIt last );
(1)
template< class ForwardIt, class BinaryPredicate >
ForwardIt unique( ForwardIt first, ForwardIt last, BinaryPredicate p );
(2)
Quita todos los elementos consecutivos duplicados de la [first, last) rango. Extracción se realiza desplazando el rango cuando sea necesario, de tal manera que los elementos que se borren se sobrescriben. Sólo el primer elemento de cada grupo de elementos iguales se deja. Los elementos entre el viejo y el nuevo final o el rango se dejan intactos. La primera versión utiliza operator== para comparar los elementos, la segunda versión utiliza el predicado binario dado p .
Original:
Removes all consecutive duplicate elements from the range [first, last). Removing is done by shifting the range when needed in such a way that elements to be erased are overwritten. Only the first element in each group of equal elements is left. The elements between the old and the new end or the range are left intact. The first version uses operator== to compare the elements, the second version uses the given binary predicate p.
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Contenido

[editar] Parámetros

first, last -
el intervalo de elementos de proceso
Original:
the range of elements to process
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p - binary predicate which returns ​true if the elements should be treated as equal.

The signature of the predicate function should be equivalent to the following:

 bool pred(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 an object of type ForwardIt can be dereferenced and then implicitly converted to both of them.

Requerimientos de tipo
-
ForwardIt debe reunir los requerimientos de ForwardIterator.
-
The type of dereferenced ForwardIt must meet the requirements of MoveAssignable.

[editar] Valor de retorno

Reenviar iterador hasta el final de la nueva gama
Original:
Forward iterator to the new end of the range
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[editar] Posible implementación

Primera versión
template<class ForwardIt>
ForwardIt unique(ForwardIt first, ForwardIt last)
{
    if (first == last)
        return last;
 
    ForwardIt result = first;
    while (++first != last) {
        if (!(*result == *first)) {
            *(++result) = *first;
        }
    }
    return ++result;
}
Segunda versión
template<class ForwardIt, class BinaryPredicate>
ForwardIt unique(ForwardIt first, ForwardIt last, 
                       BinaryPredicate p)
{
    if (first == last)
        return last;
 
    ForwardIt result = first;
    while (++first != last) {
        if (!p(*result, *first)) {
            *(++result) = *first;
        }
    }
    return ++result;
}

[editar] Ejemplo

El código siguiente quita todos los elementos consecutivos equivalentes de un vector de enteros .
Original:
The following code removes all consecutive equivalent elements from a vector of integers.
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#include <iostream>
#include <algorithm>
#include <vector>
 
int main() 
{
    std::vector<int> v{1, 2, 2, 2, 3, 3, 2, 2, 1};
    std::vector<int>::iterator last;
 
    last = std::unique(v.begin(), v.end()); // 1 2 3 2 1 3 2 2 1
                                            //           ^
    for (std::vector<int>::iterator it = v.begin(); it != last; ++it) {
        std::cout << *it << " ";
    }
    std::cout << "\n";
}

Salida:

1 2 3 2 1

[editar] Complejidad

lineal en la distancia entre first y last
Original:
linear in the distance between first and last
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[editar] Ver también

encuentra dos elementos contiguos idénticos (o que satisfacen un predicado)
(plantilla de función) [editar]
crea una copia de una cierta gama de elementos que no contiene duplicados consecutivos
Original:
creates a copy of some range of elements that contains no consecutive duplicates
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(plantilla de función) [editar]