Varianti

    std::is_permutation

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    C++
     
    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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    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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    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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    <tbody> </tbody>
    Elemento definito nell'header <algorithm>
    template< class ForwardIt1, class ForwardIt2 > bool is_permutation( ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first );
    		 (1) (dal C++11)
    template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > bool is_permutation( ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first, BinaryPredicate p );
    		 (2) (dal C++11)
    Ritorna true se esiste una permutazione degli elementi della [first1, last1) gamma che rende tale intervallo uguale all'inizio gamma a d_first. La prima versione utilizza operator== per l'uguaglianza, la seconda versione utilizza il p binario predicato
    Original:
    Returns true if there exists a permutation of the elements in the range [first1, last1) that makes that range equal to the range beginning at d_first. The first version uses operator== for equality, the second version uses the binary predicate p
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    Parametri

    first, last -
    la gamma di elementi da confrontare
    Original:
    the range of elements to compare
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    d_first -
    all'inizio del secondo intervallo da confrontare
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    the beginning of the second range to compare
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    p - binary predicate which returns ​true if the elements should be treated as equal.

    The signature of the predicate function should be equivalent to the following:

    bool pred(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 objects of types ForwardIt1 and ForwardIt2 can be dereferenced and then implicitly converted to Type1 and Type2 respectively.

    ​

    Type requirements
    -
    ForwardIt1, ForwardIt2 must meet the requirements of ForwardIterator.

    Valore di ritorno

    true se il [first, last) intervallo è una permutazione di inizio gamma a d_first.
    Original:
    true if the range [first, last) is a permutation of the range beginning at d_first.
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    Complessità

    Alla maggior parte delle applicazioni O(N2) del predicato, o esattamente N se le sequenze sono già uguali, N=std::distance(first, last) dove.
    Original:
    At most O(N2) applications of the predicate, or exactly N if the sequences are already equal, where N=std::distance(first, last).
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    Possibile implementazione

    template<class ForwardIt1, class ForwardIt2>
bool is_permutation(ForwardIt1 first, ForwardIt1 last,
                    ForwardIt2 d_first)
{
   // skip common prefix
   std::tie(first, d_first) = std::mismatch(first, last, d_first);
   // iterate over the rest, counting how many times each element
   // from [first, last) appears in [d_first, d_last)
   if (first != last) {
       ForwardIt2 d_last = d_first;
       std::advance(d_last, std::distance(first, last));
       for (ForwardIt1 i = first; i != last; ++i) {
            if (i != std::find(first, i, *i)) continue; // already counted this *i

            auto m = std::count(d_first, d_last, *i);
            if (m==0 || std::count(i, last, *i) != m) {
                return false;
            }
        }
    }
    return true;
}

    Esempio

    #include <algorithm>
#include <vector>
#include <iostream>
int main()
{
    std::vector<int> v1{1,2,3,4,5};
    std::vector<int> v2{3,5,4,1,2};
    std::cout << "3,5,4,1,2 is a permutation of 1,2,3,4,5? "
              << std::boolalpha
              << std::is_permutation(v1.begin(), v1.end(), v2.begin()) << '\n';

    std::vector<int> v3{3,5,4,1,1};
    std::cout << "3,5,4,1,1 is a permutation of 1,2,3,4,5? "
              << std::boolalpha
              << std::is_permutation(v1.begin(), v1.end(), v3.begin()) << '\n';
}

    Output: 

    3,5,4,1,2 is a permutation of 1,2,3,4,5? true
3,5,4,1,1 is a permutation of 1,2,3,4,5? false

    Vedi anche

    		 generates the next greater lexicographic permutation of a range of elements
    (funzione di modello) [modifica]
    		generates the next smaller lexicographic permutation of a range of elements
    (funzione di modello) [modifica]