std::is_permutation – cppreference.com

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definiert in Header `<algorithm>`

`template< class ForwardIt1, class ForwardIt2 > bool is_permutation( ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first );`	(1)	(seit C++11)

`template< class ForwardIt1, class ForwardIt2, class BinaryPredicate > bool is_permutation( ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first, BinaryPredicate p );`	(2)	(seit C++11)

true kehrt, wenn es eine Permutation der Elemente in dem Bereich, der [first1, last1) dass Bereichs gleich dem Bereich beginnend bei d_first macht. Die erste Version verwendet operator== für Gleichheit, nutzt die zweite Version der binären Prädikats p

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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Parameter

first, last	-	der Bereich von Elementen zu vergleichen 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	-	der Beginn des zweiten Bereichs zu vergleichen 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`.

Rückgabewert

true wenn der Bereich [first, last) ist eine Permutation der Reihe beginnend bei d_first .

Original:

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

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Komplexität

An den meisten O(N²) Anwendungen des Prädikats, oder genau N wenn die Sequenzen schon gleich, wo 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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Mögliche Implementierung

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;
}

Beispiel

#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

Siehe auch


	generates the next greater lexicographic permutation of a range of elements (Funktions-Template) [edit]

	generates the next smaller lexicographic permutation of a range of elements (Funktions-Template) [edit]