std::max_element — cppreference.com

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Déclaré dans l'en-tête `<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)

Trouve le plus grand élément de la gamme [first, last). La première version utilise operator< de comparer les valeurs, la deuxième version utilise la fonction de comparaison donnée comp .

Original:

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.

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Paramètres

first, last	-	itérateurs terme définissant la plage d'examiner Original: forward iterators defining the range to examine The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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`.

Retourne la valeur

Iterator pour le plus grand élément de la gamme [first, last). Si plusieurs éléments de la gamme sont équivalentes au plus grand élément, retourne l'itérateur sur le premier élément tel. Retours last si la plage est vide .

Original:

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.

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Complexité

Exactement max(N-1,0) comparaisons, où N = std::distance(first, last) .

Original:

Exactly max(N-1,0) comparisons, where N = std::distance(first, last).

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Mise en œuvre possible

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; }

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;
}

Exemple

#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);
}

Résultat :

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

Voir aussi


min_element	retourne le plus petit élément dans une plage 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. (fonction générique) [edit]

minmax_element (C++11)	retourne le plus petit élément et le plus important dans une gamme Original: returns the smallest and 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. (fonction générique) [edit]

max	retourne le plus grand des deux éléments Original: returns the larger of two elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]