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std::next_permutation

Da cppreference.com.
< 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 BidirIt >
bool next_permutation( BidirIt first, BidirIt last );
(1)
template< class BidirIt, class Compare >
bool next_permutation( BidirIt first, BidirIt last, Compare comp );
(2)
Trasforma il [first, last) campo nella prossima permutazione dall'insieme di tutte le permutazioni che sono classificati in ordine lessicografico rispetto al operator< o comp. true Restituisce se esiste permutazione, trasforma altrimenti il ​​campo nella prima permutazione (come per std::sort(first, last)) e ritorna false.
Original:
Transforms the range [first, last) into the next permutation from the set of all permutations that are lexicographically ordered with respect to operator< or comp. Returns true if such permutation exists, otherwise transforms the range into the first permutation (as if by std::sort(first, last)) and returns false.
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Indice

[modifica] Parametri

first, last -
la gamma di elementi per permutare
Original:
the range of elements to permute
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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 BidirIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements
-
BidirIt must meet the requirements of ValueSwappable and BidirectionalIterator.

[modifica] Valore di ritorno

true se la permutazione nuovo lessicograficamente maggiore del vecchio. false se la permutazione ultimo è stato raggiunto e la gamma è stato reimpostato per la permutazione prima.
Original:
true if the new permutation is lexicographically greater than the old. false if the last permutation was reached and the range was reset to the first permutation.
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[modifica] Complessità

Alla maggior parte degli swap N/2, dove N = std::distance(first, last).
Original:
At most N/2 swaps, where N = std::distance(first, last).
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[modifica] Possibile implementazione

template<class BidirIt>
bool next_permutation(BidirIt first, BidirIt last)
{
    if (first == last) return false;
    BidirIt i = last;
    if (first == --i) return false;
 
    while (1) {
        BidirIt i1, i2;
 
        i1 = i;
        if (*--i < *i1) {
            i2 = last;
            while (!(*i < *--i2))
                ;
            std::iter_swap(i, i2);
            std::reverse(i1, last);
            return true;
        }
        if (i == first) {
            std::reverse(first, last);
            return false;
        }
    }
}

[modifica] Esempio

Il codice seguente consente di stampare tutte e tre le permutazioni della stringa "aba"
Original:
The following code prints all three permutations of the string "aba"
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#include <algorithm>
#include <string>
#include <iostream>
 
int main()
{
    std::string s = "aba";
    std::sort(s.begin(), s.end());
    do {
        std::cout << s << '\n';
    } while(std::next_permutation(s.begin(), s.end()));
}

Output:

aab
aba
baa

[modifica] Vedi anche

determines if a sequence is a permutation of another sequence
(funzione di modello) [edit]
generates the next smaller lexicographic permutation of a range of elements
(funzione di modello) [edit]