std::nth_element — cppreference.com

De cppreference.com

Déclaré dans l'en-tête `<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.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Paramètres

first, last	-	itérateurs d'accès aléatoire définissant le type plage Original: random access iterators defining the range sort The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
nth	-	itérateur à accès aléatoire définissant le point de partition genre Original: random access iterator defining the sort partition point The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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`.

Retourne la valeur

(Aucun)

Original:

(none)

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Complexité

Linéaire dans std::distance(first, last) en moyenne .

Original:

Linear in std::distance(first, last) on average.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

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

Voir aussi


partial_sort_copy	copies et partiellement Trie une plage d'éléments Original: copies and partially sorts a range of elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]

stable_sort	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 The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]

sort	trie une plage dans l'ordre ascendant Original: sorts a range into ascending order The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]