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std::minmax_element

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)
minmax_element
(C++11)
(C++17)
Permutaciones
Operaciones numéricas
Bibliotecas C
 
Definido en la cabecera <algorithm>
template< class ForwardIt >

std::pair<ForwardIt,ForwardIt>

    minmax_element( ForwardIt first, ForwardIt last );
(1)
template< class ForwardIt, class Compare >

std::pair<ForwardIt,ForwardIt>

    minmax_element( ForwardIt first, ForwardIt last, Compare comp );
(2)
Encuentra el más grande y el más pequeño elemento de la [first, last) rango. La primera versión utiliza operator< para comparar los valores, la segunda versión utiliza la función de comparación dado comp .
Original:
Finds the greatest and the smallest element in the range [first, last). The first version uses operator< to compare the values, the second version uses the given comparison function comp.
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Contenido

[editar] Parámetros

first, last -
iteradores hacia adelante que definen el rango de examinar
Original:
forward iterators defining the range to examine
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cmp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if if *a is less than *b.

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

 bool cmp(const Type1 &a, const Type2 &b);

While the signature does not need to have const &, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1 & is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy (desde C++11)).
The types Type1 and Type2 must be such that an object of type ForwardIt can be dereferenced and then implicitly converted to both of them. ​

Requerimientos de tipo
-
ForwardIt debe reunir los requerimientos de ForwardIterator.

[editar] Valor de retorno

un par formado por un iterador al elemento más pequeño como el primer elemento y un iterador al elemento más grande que la segunda. Devoluciones std::make_pair(first, first) si el rango está vacía. Si varios elementos son equivalentes para el elemento más pequeño, el iterador al elemento tal primero se devuelve. Si varios elementos son equivalentes para el elemento más grande, el iterador al elemento tal se devolverá el último .
Original:
a pair consisting of an iterator to the smallest element as the first element and an iterator to the greatest element as the second. Returns std::make_pair(first, first) if the range is empty. If several elements are equivalent to the smallest element, the iterator to the first such element is returned. If several elements are equivalent to the largest element, the iterator to the last such element is returned.
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[editar] Complejidad

En la mayoría de las aplicaciones max(floor(3/2(N−1)), 0) del predicado, donde N = std::distance(first, last) .
Original:
At most max(floor(3/2(N−1)), 0) applications of the predicate, where N = std::distance(first, last).
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[editar] Posible implementación

Primera versión
template<class ForwardIt>
std::pair<ForwardIt, ForwardIt> 
    minmax_element(ForwardIt first, ForwardIt last)
{
    typedef typename std::iterator_traits<ForwardIt>::value_type value_t;
    return std::minmax_element(first, last, std::less<value_t>());
}
Segunda versión
template<class ForwardIt, class Compare>
std::pair<ForwardIt, ForwardIt> 
    minmax_element(ForwardIt first, ForwardIt last, Compare comp)
{
    std::pair<ForwardIt, ForwardIt> result(first, first);
 
    if (first == last) return result;
    if (++first == last) return result;
 
    if (comp(*first, *result.first)) {
        result.second = result.first;
        result.first = first;
    } else {
        result.second = first;
    }
    while (++first != last) {
        ForwardIt i = first;
        if (++first == last) {
            if (comp(*i, *result.first)) result.first = i;
            else if (!(comp(*i, *result.second))) result.second = i;
            break;
        } else {
            if (comp(*first, *i)) {
                if (comp(*first, *result.first)) result.first = first;
                if (!(comp(*i, *result.second))) result.second = i;
            } else {
                if (comp(*i, *result.first)) result.first = i;
                if (!(comp(*first, *result.second))) result.second = first;
            }
        }
    }
    return result;
}

[editar] Ejemplo

#include <algorithm>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v = { 3, 9, 1, 4, 2, 5, 9 };
 
    auto result = std::minmax_element(v.begin(), v.end());
    std::cout << "min element at: " << (result.first - v.begin()) << '\n';
    std::cout << "max element at: " << (result.second - v.begin()) << '\n';
}

Salida:

min element at: 2
max element at: 6

[editar] Ver también

devuelve el elemento más pequeño de un rango
Original:
returns the smallest element in a range
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(plantilla de función) [editar]
devuelve el elemento más grande de un rango
Original:
returns the largest element in a range
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(plantilla de función) [editar]