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std::partition

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Bibliothèque d'algorithmes
Fonctions
Original:
Functions
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Non-modification de la séquence des opérations
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Non-modifying sequence operations
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Modification de la séquence des opérations
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Modifying sequence operations
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Des opérations de partitionnement
Original:
Partitioning operations
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is_partitioned (C++11)
partition
partition_copy (C++11)
Opérations de tri (sur les gammes triés)
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Sorting operations (on sorted ranges)
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is_sorted (C++11)
is_sorted_until (C++11)
sort
Opérations binaires de recherche (sur les gammes triés)
Original:
Binary search operations (on sorted ranges)
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Définir les opérations (sur les gammes triés)
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Set operations (on sorted ranges)
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Opérations Heap
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Heap operations
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Minimum / maximum de fonctionnement
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Minimum/maximum operations
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Opérations numériques
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Numeric operations
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Bibliothèque C
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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 );
(avant C++11)

(depuis C++11)
Réordonne les éléments de la gamme [first, last) de telle manière que tous les éléments pour lesquels le prédicat renvoie p true précéder les éléments pour lesquels prédicat retourne p false. Ordre relatif des éléments ne sont pas conservées .
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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Sommaire

[modifier] Paramètres

first, last -
l'éventail d'éléments à réorganiser
Original:
the range of elements to reorder
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p - unary predicate which returns ​true
si l'élément doit être commandé avant autres éléments
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

[modifier] Retourne la valeur

Itérateur sur le premier élément du second groupe .
Original:
Iterator to the first element of the second group.
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[modifier] Complexité

Exactement last-first applications du prédicat et à la plupart des swaps last-first. Si ForwardIt répond aux exigences de la plupart des swaps BidirectionalIterator à (last-first)/2 sont fait .
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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[modifier] Mise en œuvre possible

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;
}

[modifier] Exemple

#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, " "));
}

Résultat possible :

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

[modifier] Voir aussi

détermine si l'intervalle est divisé par le prédicat donné
Original:
determines if the range is partitioned by the given predicate
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(fonction générique) [edit]
divise les éléments en deux groupes, tout en préservant leur ordre relatif
Original:
divides elements into two groups while preserving their relative order
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(fonction générique) [edit]