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std::max_element

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< cpp‎ | algorithm

 
 
Biblioteca algoritmo
Funções
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Functions
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Não modificar operações de seqüência
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Non-modifying sequence operations
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Modificando operações de seqüência
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Modifying sequence operations
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Particionamento operações
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Partitioning operations
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Operações de classificação (em intervalos ordenados)
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Sorting operations (on sorted ranges)
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Binários operações de busca (em intervalos ordenados)
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Binary search operations (on sorted ranges)
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Definir operações (em intervalos ordenados)
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Set operations (on sorted ranges)
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Operações de pilha
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Heap operations
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Mínimo / máximo de operações
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Minimum/maximum operations
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max
max_element
min
min_element
minmax(C++11)
minmax_element(C++11)
Operações numéricas
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Numeric operations
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C biblioteca
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C library
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Defined in header <algorithm>
template< class ForwardIt >
ForwardIt max_element( ForwardIt first, ForwardIt last );
(1)
template< class ForwardIt, class Compare >
ForwardIt max_element( ForwardIt first, ForwardIt last, Compare comp );
(2)

Finds the greatest element in the range [first, last). The first version uses operator< to compare the values, the second version uses the given comparison function comp.

Índice

[editar] Parâmetros

first, last -
iteradores para a frente que definem o intervalo para examinar
Original:
forward iterators defining the range to examine
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cmp - comparison function 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);

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 an object of type ForwardIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements
-
ForwardIt must meet the requirements of ForwardIterator.

[editar] Valor de retorno

Iterator to the greatest element in the range [first, last). If several elements in the range are equivalent to the greatest element, returns the iterator to the first such element. Returns last if the range is empty.

[editar] Complexidade

Exactamente max(N-1,0) comparações, onde N = std::distance(first, last).
Original:
Exactly max(N-1,0) comparisons, where N = std::distance(first, last).
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[editar] Possível implementação

First version
template<class ForwardIt>
ForwardIt max_element(ForwardIt first, ForwardIt last)
{
    if (first == last) {
        return last;
    }
    ForwardIt largest = first;
    ++first;
    for (; first != last; ++first) {
        if (*largest < *first) {
            largest = first;
        }
    }
    return largest;
}
Second version
template<class ForwardIt, class Compare>
ForwardIt max_element(ForwardIt first, ForwardIt last, 
                            Compare comp)
{
    if (first == last) {
        return last;
    }
    ForwardIt largest = first;
    ++first;
    for (; first != last; ++first) {
        if (comp(*largest, *first)) {
            largest = first;
        }
    }
    return largest;
}

[editar] Exemplo

#include <algorithm>
#include <iostream>
#include <vector>
#include <cmath>
 
static bool abs_compare(int a, int b)
{
    return (std::abs(a) < std::abs(b));
}
 
int main()
{
    std::vector<int> v{ 3, 1, -14, 1, 5, 9 }; 
    std::vector<int>::iterator result;
 
    result = std::max_element(v.begin(), v.end());
    std::cout << "max element at: " << std::distance(v.begin(), result) << '\n';
 
    result = std::max_element(v.begin(), v.end(), abs_compare);
    std::cout << "max element (absolute) at: " << std::distance(v.begin(), result);
}

Output:

max element at: 5
max element (absolute) at: 2

[editar] Veja também

retorna o elemento mais pequeno de um intervalo
Original:
returns the smallest element in a range
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(modelo de função) [edit]
retorna o elemento menor e maior em um intervalo
Original:
returns the smallest and the largest element in a range
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(modelo de função) [edit]
devolve o maior dos dois elementos
Original:
returns the larger of two elements
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(modelo de função) [edit]