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std::partition

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< cpp‎ | algorithm

 
 
Algoritmo biblioteca
Funciones
Original:
Functions
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Para no modificar la secuencia de las operaciones
Original:
Non-modifying sequence operations
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Modificación de la secuencia de operaciones
Original:
Modifying sequence operations
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Particionamiento operaciones
Original:
Partitioning operations
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is_partitioned(C++11)
partition
partition_copy(C++11)
Clasificación de las operaciones (en rangos ordenados)
Original:
Sorting operations (on sorted ranges)
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Las operaciones binarias de búsqueda (en rangos ordenados)
Original:
Binary search operations (on sorted ranges)
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Conjunto de operaciones (en rangos ordenados)
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Set operations (on sorted ranges)
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Operaciones del montón
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Heap operations
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Mínimo / máximo de operaciones
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Minimum/maximum operations
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Operaciones numéricas
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Numeric operations
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C biblioteca
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C library
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Defined in header <algorithm>
template< class BidirIt, class UnaryPredicate >

BidirectionalIterator partition( BidirIt first, BidirIt last,
                                 UnaryPredicate p );
template< class ForwardIt, class UnaryPredicate >
ForwardIt partition( ForwardIt first, ForwardIt last,

                     UnaryPredicate p );
(hasta C++11)

(desde C++11)
Reordena los elementos de la [first, last) rango de tal manera que todos los elementos para los que el predicado p vuelve true preceder a los elementos para los que predicado p vuelve false. Orden relativo de los elementos no se conserva .
Original:
Reorders the elements in the range [first, last) in such a way that all elements for which the predicate p returns true precede the elements for which predicate p returns false. Relative order of the elements is not preserved.
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Contenido

[editar] Parámetros

first, last -
la gama de elementos a ordenar
Original:
the range of elements to reorder
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p - unary predicate which returns ​true
si el elemento debe pedirse antes de otros elementos
Original:
if the element should be ordered before other elements
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.

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

 bool pred(const Type &a);

The signature does not need to have const &, but the function must not modify the objects passed to it.
The type Type must be such that an object of type ForwardIt can be dereferenced and then implicitly converted to Type. ​

Type requirements
-
BidirIt must meet the requirements of BidirectionalIterator.
-
ForwardIt must meet the requirements of ValueSwappable and ForwardIterator. However, the operation is more efficient if ForwardIt also satisfies the requirements of BidirectionalIterator

[editar] Valor de retorno

Iterador al primer elemento del segundo grupo .
Original:
Iterator to the first element of the second group.
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[editar] Complejidad

Exactamente last-first aplicaciones del predicado y en la mayoría de los swaps last-first. Si ForwardIt cumple los requisitos de BidirectionalIterator en la mayoría de los swaps (last-first)/2 se hacen .
Original:
Exactly last-first applications of the predicate and at most last-first swaps. If ForwardIt meets the requirements of BidirectionalIterator at most (last-first)/2 swaps are done.
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[editar] Posible implementación

template<class BidirIt, class UnaryPredicate>
BidirIt partition(BidirIt first, BidirIt last, UnaryPredicate p)
{
    while (1) {
        while ((first != last) && p(*first)) {
            ++first;
        }
        if (first == last--) break;
        while ((first != last) && !p(*last)) {
            --last;
        }
        if (first == last) break;
        std::swap(*first++, *last);
    }
    return first;
}

[editar] Ejemplo

#include <algorithm>
#include <functional>
#include <iostream>
#include <iterator>
#include <vector>
 
bool is_even(int i) { return i % 2 == 0; }
 
int main()
{
    std::vector<int> v;
    for (int i = 0; i < 10; ++i) v.push_back(i);
 
    std::cout << "Original vector:\n    ";
    std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " "));
 
    // Partition the vector
    std::vector<int>::iterator p =
        std::partition(v.begin(), v.end(), std::ptr_fun(is_even));
 
    std::cout << "\nPartitioned vector:\n    ";
    std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\nBefore partition:\n    ";
    std::copy(v.begin(), p,       std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\nAfter partition:\n    ";
    std::copy(p,         v.end(), std::ostream_iterator<int>(std::cout, " "));
}

Possible output:

Original vector:
    0 1 2 3 4 5 6 7 8 9 
Partitioned vector:
    0 8 2 6 4 5 3 7 1 9 
Before partition:
    0 8 2 6 4 
After partition:
    5 3 7 1 9

[editar] Ver también

determina si el intervalo está dividido por el predicado dado
Original:
determines if the range is partitioned by the given predicate
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(función de plantilla) [edit]
elementos divide en dos grupos, preservando su orden relativo
Original:
divides elements into two groups while preserving their relative order
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(función de plantilla) [edit]