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std::nth_element

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< cpp‎ | algorithm

 
 
Bibliothèque d'algorithmes
Fonctions
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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
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Partitioning operations
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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)
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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 RandomIt >
void nth_element( RandomIt first, RandomIt nth, RandomIt last );
(1)
template< class RandomIt, class Compare >
void nth_element( RandomIt first, RandomIt nth, RandomIt last, Compare comp );
(2)
Partiellement sortes [first, last) la plage dans l'ordre croissant de sorte que tous les éléments de la gamme sont [first, nth) moins que ceux de la gamme [nth, last). La première version utilise operator< de comparer les éléments, la deuxième version utilise la fonction de comparaison donnée comp. L'élément placé dans la position nth est exactement l'élément qui se produirait dans cette position si la gamme a été entièrement trié .
Original:
Partially sorts the range [first, last) in ascending order so that all elements in the range [first, nth) are less than those in the range [nth, last). The first version uses operator< to compare the elements, the second version uses the given comparison function comp. The element placed in the nth position is exactly the element that would occur in this position if the range was fully sorted.
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Sommaire

[modifier] Paramètres

first, last -
itérateurs d'accès aléatoire définissant le type plage
Original:
random access iterators defining the range sort
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nth -
itérateur à accès aléatoire définissant le point de partition genre
Original:
random access iterator defining the sort partition point
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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 types Type1 and Type2 must be such that an object of type RandomIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements
-
RandomIt must meet the requirements of ValueSwappable and RandomAccessIterator.
-
The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.

[modifier] Retourne la valeur

(Aucun)
Original:
(none)
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[modifier] Complexité

Linéaire dans std::distance(first, last) en moyenne .
Original:
Linear in std::distance(first, last) on average.
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[modifier] Exemple

#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
 
int main()
{
    std::vector<int> v{5, 6, 4, 3, 2, 6, 7, 9, 3};
 
    std::nth_element(v.begin(), v.begin() + v.size()/2, v.end());
    std::cout << "The median is " << v[v.size()/2] << '\n';
 
    std::nth_element(v.begin(), v.begin()+1, v.end(), std::greater<int>());
    std::cout << "The second largest element is " << v[1] << '\n';
}

Résultat :

The median is 5
The second largest element is 7

[modifier] Voir aussi

copies et partiellement Trie une plage d'éléments
Original:
copies and partially sorts a range of elements
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(fonction générique) [edit]
Trie une plage d'éléments, tout en préservant l'ordre entre des éléments égaux
Original:
sorts a range of elements while preserving order between equal elements
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(fonction générique) [edit]
trie une plage dans l'ordre ascendant
Original:
sorts a range into ascending order
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(fonction générique) [edit]