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std::max_element

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Non-modifying sequence operations
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Sorting operations (on sorted ranges)
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max
max_element
min
min_element
minmax(C++11)
minmax_element(C++11)
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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.

Inhaltsverzeichnis

[Bearbeiten] Parameter

first, last -
Vorwärts Iteratoren definieren den Bereich zu prüfen
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.

[Bearbeiten] Rückgabewert

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.

[Bearbeiten] Komplexität

Genau max(N-1,0) Vergleiche, wo N = std::distance(first, last) .
Original:
Exactly max(N-1,0) comparisons, where N = std::distance(first, last).
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[Bearbeiten] Mögliche Implementierung

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;
}

[Bearbeiten] Beispiel

#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

[Bearbeiten] Siehe auch

gibt das kleinste Element in einem Bereich
Original:
returns the smallest element in a range
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(Funktions-Template) [edit]
gibt die kleinste und das größte Element in einem Bereich
Original:
returns the smallest and the largest element in a range
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(Funktions-Template) [edit]
liefert den größeren der beiden Elemente
Original:
returns the larger of two elements
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(Funktions-Template) [edit]