std::is_permutation — cppreference.com

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Déclaré dans l'en-tête `<algorithm>`
`template< class ForwardIt1, class ForwardIt2 > bool is_permutation( ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first );`	(1)	(depuis C++11)
`template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > bool is_permutation( ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first, BinaryPredicate p );`	(2)	(depuis C++11)

Retours true s'il existe une permutation des éléments de la gamme [first1, last1) qui rend cet intervalle égal à l'intervalle commençant à d_first. La première version utilise operator== pour l'égalité, la deuxième version utilise le p prédicat binaire

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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Paramètres

first, last	-	la plage d'éléments à comparer Original: the range of elements to compare The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
d_first	-	le début de la deuxième plage de comparer Original: the beginning of the second range to compare The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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`.

Retourne la valeur

true si le [first, last) plage est une permutation de la gamme débutant à d_first .

Original:

true if the range [first, last) is a permutation of the range beginning at d_first.

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Complexité

À la plupart des applications O(N²) du prédicat, ou exactement N si les séquences sont déjà égaux, où N=std::distance(first, last) .

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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Mise en œuvre possible

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;
}

Exemple

#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';
}

Résultat :

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

Voir aussi


	génère la plus grande lexicographique prochaine permutation d'un ensemble d'éléments Original: generates the next greater lexicographic permutation of a range of elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]

	lexicographique génère le plus petit côté d'une permutation série d'éléments Original: generates the next smaller lexicographic permutation of a range of elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]