std::partition
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<tbody> </tbody>| Elemento definito nell'header <algorithm>
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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 ); |
(fino al c++11) (dal C++11) |
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Riordina gli elementi nel
[first, last) gamma in modo tale che tutti gli elementi per cui il predicato p rendimenti true precedere gli elementi per i quali predicato p rendimenti false. Ordine relativo degli elementi non è conservato. 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. The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
You can help to correct and verify the translation. Click here for instructions.
Parametri
| first, last | - | la gamma di elementi da riordinare
Original: the range of elements to reorder The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| p | - | unary predicate which returns true se l'elemento deve essere ordinato prima di altri elementi . Original: if the element should be ordered before other elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. The signature of the predicate function should be equivalent to the following:
The signature does not need to have |
| Type requirements | ||
-BidirIt must meet the requirements of BidirectionalIterator.
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-ForwardIt must meet the requirements of ValueSwappable and ForwardIterator. However, the operation is more efficient if ForwardIt also satisfies the requirements of BidirectionalIterator
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Valore di ritorno
Iteratore al primo elemento del secondo gruppo.
Original:
Iterator to the first element of the second group.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
You can help to correct and verify the translation. Click here for instructions.
Complessità
Esattamente
last-first applicazioni del predicato e la maggior parte delle operazioni di swap last-first. Se ForwardIt soddisfa i requisiti della maggior parte delle operazioni di swap in BidirectionalIterator (last-first)/2 sono fatte.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.The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
You can help to correct and verify the translation. Click here for instructions.
Possibile implementazione
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;
}
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Esempio
#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
Vedi anche
(C++11) |
determina se il campo è diviso dal predicato specificato Original: determines if the range is partitioned by the given predicate The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello) |
divide gli elementi in due gruppi, mantenendo l'ordine relativo Original: divides elements into two groups while preserving their relative order The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello) | |
