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std::prev_permutation

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< cpp‎ | algorithm

 
 
Biblioteca algoritmo
Funções
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Functions
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Não modificar operações de seqüência
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Non-modifying sequence operations
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Modificando operações de seqüência
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Modifying sequence operations
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Particionamento operações
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Partitioning operations
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Operações de classificação (em intervalos ordenados)
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Sorting operations (on sorted ranges)
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Binários operações de busca (em intervalos ordenados)
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Binary search operations (on sorted ranges)
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Definir operações (em intervalos ordenados)
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Set operations (on sorted ranges)
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Operações de pilha
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Heap operations
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Mínimo / máximo de operações
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Minimum/maximum operations
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Operações 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 o [first, last) intervalo na permutação anterior a partir do conjunto de todas as permutações que são lexicographically ordenadas em relação a operator< ou comp. Retorna true se existe tal permutação, caso contrário, transforma o intervalo na última permutação (como se por std::sort(first, last); std::reverse(first, last);) e retorna 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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Índice

[editar] Parâmetros

first, last -
a gama de elementos para 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 se a permutação nova precede a idade em lexicográfico ordem. false se a permutação primeiro foi alcançado ea gama foi redefinido para a permutação passado.
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] Complexidade

Na maioria dos swaps (last-first)/2.
Original:
At most (last-first)/2 swaps.
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[editar] Possível implementação

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] Exemplo

O código a seguir imprime todas as seis permutações da cadeia "ABC" em ordem inversa
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] Veja também

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