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std::is_permutation

De cppreference.com
< cpp‎ | algorithm
 
 
Biblioteca de algoritmos
Políticas de ejecución (C++17)
Operaciones no modificadoras de secuencia
(C++11)(C++11)(C++11)
(C++17)
Operaciones modificadoras de secuencia
Operaciones en almacenamiento no inicializado
Operaciones de partición
Operaciones de ordenación
(C++11)
Operaciones de búsqueda binaria
Operaciones de set (en rangos ordenados)
Operaciones de pila
(C++11)
Operaciones minimo/maximo
(C++11)
(C++17)
Permutaciones
is_permutation
(C++11)
Operaciones numéricas
Bibliotecas C
 
Definido en la cabecera <algorithm>
template< class ForwardIt1, class ForwardIt2 >

bool is_permutation( ForwardIt1 first, ForwardIt1 last,

                     ForwardIt2 d_first );
(1) (desde C++11)
template< class ForwardIt1, class ForwardIt2, class BinaryPredicate >

bool is_permutation( ForwardIt1 first, ForwardIt1 last,

                     ForwardIt2 d_first, BinaryPredicate p );
(2) (desde C++11)
Regreso true si existe una permutación de los elementos en el rango [first1, last1) que hace que rango igual al rango de principio a d_first. La primera versión utiliza operator== por la igualdad, la segunda versión utiliza el p predicado binario
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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Contenido

[editar] Parámetros

first, last -
el intervalo de elementos para comparar
Original:
the range of elements to compare
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d_first -
el comienzo de la segunda gama de comparar
Original:
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.

Requerimientos de tipo
-
ForwardIt1, ForwardIt2 debe reunir los requerimientos de ForwardIterator.

[editar] Valor de retorno

true si la [first, last) rango es una permutación del rango de principio a d_first .
Original:
true if the range [first, last) is a permutation of the range beginning at d_first.
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[editar] Complejidad

En la mayoría de las aplicaciones O(N2) del predicado, o exactamente N si las secuencias son ya iguales, N=std::distance(first, last) donde .
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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[editar] Posible implementación

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;
}

[editar] Ejemplo

#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';
}

Salida:

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

[editar] Ver también

generates the next greater lexicographic permutation of a range of elements
(plantilla de función) [editar]
generates the next smaller lexicographic permutation of a range of elements
(plantilla de función) [editar]