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std::max_element

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< cpp‎ | algorithm

 
 
Bibliothèque d'algorithmes
Fonctions
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Functions
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Non-modification de la séquence des opérations
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Non-modifying sequence operations
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Modification de la séquence des opérations
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Modifying sequence operations
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Des opérations de partitionnement
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Partitioning operations
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Opérations de tri (sur les gammes triés)
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Sorting operations (on sorted ranges)
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is_sorted (C++11)
is_sorted_until (C++11)
sort
Opérations binaires de recherche (sur les gammes triés)
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Binary search operations (on sorted ranges)
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Définir les opérations (sur les gammes triés)
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Set operations (on sorted ranges)
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Opérations Heap
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Heap operations
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Minimum / maximum de fonctionnement
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Minimum/maximum operations
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max
max_element
min
min_element
minmax (C++11)
minmax_element (C++11)
Opérations numériques
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Numeric operations
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Bibliothèque C
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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)
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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Sommaire

[modifier] Paramètres

first, last -
itérateurs terme définissant la plage d'examiner
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.

[modifier] 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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[modifier] 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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[modifier] 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;
}

[modifier] 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

[modifier] Voir aussi

retourne le plus petit élément dans une plage
Original:
returns the smallest element in a range
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(fonction générique) [edit]
retourne le plus petit élément et le plus important dans une gamme
Original:
returns the smallest and the largest element in a range
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(fonction générique) [edit]
retourne le plus grand des deux éléments
Original:
returns the larger of two elements
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(fonction générique) [edit]