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std::next_permutation

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Algorithm Bibliothek
Funktionen
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Functions
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Nicht-modifizierende Sequenz Operationen
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Non-modifying sequence operations
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Modifizierende Sequenz Operationen
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Modifying sequence operations
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Partitionierungsoperationen
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Partitioning operations
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Sortierung Operationen (auf sortierten Bereiche)
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Sorting operations (on sorted ranges)
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Binary Suchaktionen (auf sortierten Bereiche)
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Binary search operations (on sorted ranges)
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Set-Operationen (auf sortierten Bereiche)
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Set operations (on sorted ranges)
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Heap-Operationen
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Heap operations
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Minimum / Maximum Operationen
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Minimum/maximum operations
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Numerische Operationen
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Numeric operations
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C-Bibliothek
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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)
Transformiert den Bereich [first, last) in die nächste Permutation aus der Menge aller Permutationen, lexikographisch bezüglich operator< oder comp geordnet sind. Versandkosten true wenn solche Permutation existiert, sonst wandelt den Bereich in der ersten Permutation (wie von std::sort(first, last)) und kehrt 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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Inhaltsverzeichnis

[Bearbeiten] Parameter

first, last -
das Spektrum der Elemente vertauschen
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.

[Bearbeiten] Rückgabewert

true wenn die neue Permutation ist lexikographisch größer als der alte. false wenn die letzte Permutation erreicht wurde und der Bereich wurde zurückgesetzt, um die erste Permutation .
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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[Bearbeiten] Komplexität

An den meisten N/2 Swaps, wo N = std::distance(first, last) .
Original:
At most N/2 swaps, where N = std::distance(first, last).
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[Bearbeiten] Mögliche Implementierung

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;
        }
    }
}

[Bearbeiten] Beispiel

Der folgende Code gibt alle drei Permutationen der Zeichenfolge "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

[Bearbeiten] Siehe auch

determines if a sequence is a permutation of another sequence
(Funktions-Template) [edit]
generates the next smaller lexicographic permutation of a range of elements
(Funktions-Template) [edit]