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std::nth_element

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< cpp‎ | algorithm

 
 
Algoritmo libreria
Funzioni
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Functions
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Non modifica le operazioni di sequenza
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Non-modifying sequence operations
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Modifica delle operazioni di sequenza
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Modifying sequence operations
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Partizionamento operazioni
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Partitioning operations
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Ordinamento delle operazioni (su intervalli ordinati)
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Sorting operations (on sorted ranges)
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Binarie (le operazioni di ricerca sui campi ordinati)
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Binary search operations (on sorted ranges)
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Impostare le operazioni (su intervalli ordinati)
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Set operations (on sorted ranges)
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Heap operazioni
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Heap operations
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Minimo / massimo le operazioni
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Minimum/maximum operations
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Operazioni numeriche
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Numeric operations
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Libreria 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)
Parzialmente ordina la [first, last) intervallo in ordine crescente in modo che tutti gli elementi della gamma [first, nth) sono meno rispetto a quelli del [nth, last) gamma. La prima versione utilizza operator< di confrontare gli elementi, la seconda versione utilizza la data comp funzione di confronto. L'elemento posto in posizione nth è esattamente l'elemento che si verificano in questa posizione se l'intervallo è stato completamente ordinato.
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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Indice

[modifica] Parametri

first, last -
iteratori ad accesso casuale che definiscono il tipo gamma
Original:
random access iterators defining the range sort
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nth -
iteratore ad accesso casuale la definizione del punto di partizione ordinamento
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.

[modifica] Valore di ritorno

(Nessuno)
Original:
(none)
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[modifica] Complessità

Lineare in std::distance(first, last) in media.
Original:
Linear in std::distance(first, last) on average.
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[modifica] Esempio

#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';
}

Output:

The median is 5
The second largest element is 7

[modifica] Vedi anche

copie e parzialmente ordina una serie di elementi
Original:
copies and partially sorts a range of elements
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(funzione di modello) [edit]
Ordina un intervallo di elementi, mantenendo ordine tra elementi uguali
Original:
sorts a range of elements while preserving order between equal elements
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(funzione di modello) [edit]
ordina una serie in ordine crescente
Original:
sorts a range into ascending order
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(funzione di modello) [edit]