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std::prev_permutation

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< cpp‎ | algorithm

 
 
Algoritmo biblioteca
Funciones
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Functions
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Para no modificar la secuencia de las operaciones
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Non-modifying sequence operations
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Modificación de la secuencia de operaciones
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Modifying sequence operations
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Particionamiento operaciones
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Partitioning operations
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Clasificación de las operaciones (en rangos ordenados)
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Sorting operations (on sorted ranges)
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Las operaciones binarias de búsqueda (en rangos ordenados)
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Binary search operations (on sorted ranges)
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Conjunto de operaciones (en rangos ordenados)
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Set operations (on sorted ranges)
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Operaciones del montón
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Heap operations
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Mínimo / máximo de operaciones
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Minimum/maximum operations
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Operaciones numéricas
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Numeric operations
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C biblioteca
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C library
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Defined in header <algorithm>
template< class BidirIt >
bool prev_permutation( BidirIt first, BidirIt last);
(1)
template< class BidirIt, class Compare >
bool prev_permutation( BidirIt first, BidirIt last, Compare comp);
(2)
Transforma el [first, last) gama en la permutación anterior a partir del conjunto de todas las permutaciones que están ordenadas lexicográficamente con respecto a operator< o comp. true Devuelve si existe tal permutación, de lo contrario se transforma en el rango de la permutación final (como por std::sort(first, last); std::reverse(first, last);) y vuelve false .
Original:
Transforms the range [first, last) into the previous 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 last permutation (as if by std::sort(first, last); std::reverse(first, last);) and returns false.
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Contenido

[editar] Parámetros

first, last -
el intervalo de elementos de permutar
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.

[editar] Valor de retorno

true si la nueva permutación precede a la edad en orden lexicográfico. false si la primera permutación fue alcanzado y el intervalo de puesta a cero a la última permutación .
Original:
true if the new permutation precedes the old in lexicographical order. false if the first permutation was reached and the range was reset to the last permutation.
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[editar] Complejidad

En la mayoría de los swaps (last-first)/2 .
Original:
At most (last-first)/2 swaps.
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[editar] Posible implementación

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

[editar] Ejemplo

El siguiente código imprime los seis permutaciones de la cadena "abc" en orden inverso
Original:
The following code prints all six permutations of the string "abc" in reverse order
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#include <algorithm>
#include <string>
#include <iostream>
#include <functional>
int main()
{
    std::string s="abc";
    std::sort(s.begin(), s.end(), std::greater<char>());
    do {
        std::cout << s << ' ';
    } while(std::prev_permutation(s.begin(), s.end()));
    std::cout << '\n';
}

Output:

cba cab bca bac acb abc

[editar] Ver también

determines if a sequence is a permutation of another sequence
(función de plantilla) [edit]
prev_permutation
generates the next smaller lexicographic permutation of a range of elements
(función de plantilla) [edit]