std::count, std::count_if

 

C++

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Concepts

Bibliothèque d'utilitaires

Bibliothèque pour les chaînes de caractères

Bibliothèque de conteneurs

Bibliothèque d'algorithmes

Bibliothèque d'itérateurs

Bibliothèque pour le calcul numérique

Bibliothèque pour les entrées/sorties

Bibliothèque pour la régionalisation

Bibliothèque pour les expressions régulières (C++11)

Bibliothèque pour les opérations atomiques (C++11)

Bibliothèque pour les processus légers (threads) (C++11)

 

Bibliothèque d'algorithmes

Fonctions Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Non-modification de la séquence des opérations Original: Non-modifying sequence operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
all_of any_of none_of (C++11) (C++11) (C++11) for_each count count_if mismatch equal	find find_if find_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modification de la séquence des opérations Original: Modifying sequence operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
copy copy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   (C++11) unique unique_copy
Des opérations de partitionnement Original: Partitioning operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
Opérations de tri (sur les gammes triés) Original: Sorting operations (on sorted ranges) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
Opérations binaires de recherche (sur les gammes triés) Original: Binary search operations (on sorted ranges) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
lower_bound upper_bound	binary_search equal_range
Définir les opérations (sur les gammes triés) Original: Set operations (on sorted ranges) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
Opérations Heap Original: Heap operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
is_heap is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
Minimum / maximum de fonctionnement Original: Minimum/maximum operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
max max_element min min_element minmax (C++11) minmax_element (C++11)	lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
Opérations numériques Original: Numeric operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
iota (C++11) accumulate inner_product	adjacent_difference partial_sum
Bibliothèque C Original: C library The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
qsort	bsearch

 

Déclaré dans l'en-tête <algorithm>
template<class InputIt, class T > typename iterator_traits<InputIt>::difference_type     count( InputIt first, InputIt last, const T &value );	(1)
template<class InputIt, class UnaryPredicate > typename iterator_traits<InputIt>::difference_type     count_if( InputIt first, InputIt last, UnaryPredicate p );	(2)

Retourne le nombre d'éléments dans la gamme [first, last) satisfaisant des critères spécifiques. La première version compte les éléments qui sont égaux à value, la deuxième version compte les éléments pour lesquels prédicat retourne ptrue .

Original:

Returns the number of elements in the range [first, last) satisfying specific criteria. The first version counts the elements that are equal to value, the second version counts elements for which predicate p returns true.

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Paramètres

first, last	-	l'éventail des éléments à examiner Original: the range of elements to examine The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
value	-	la valeur à rechercher Original: the value to search for The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
p	-	prédicat unéaire qui retourne ​true pour les éléments requis Original: for the required elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. . L'expression p(v) doit pouvoir être convertie à bool pour tout argument v de type (possiblement const) VT, où VT est le type de valeur de InputIt, inconditionellement de value category, et ne doit pas modifier v. Ainsi, un type-paramètre VT&n'est pas permis ainsi que pour VT sauf pour VT un déplacement est équivalent à une copie (depuis C++11). ​
Type requirements
- InputIt must meet the requirements of InputIterator.

Retourne la valeur

certain nombre d'éléments satisfaisant la condition .

Original:

number of elements satisfying the condition.

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Complexité

exactement last - first comparaisons / applications du prédicat

Original:

exactly last - first comparisons / applications of the predicate

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Mise en œuvre possible

First version
template<class InputIt, class T>typename iterator_traits<InputIt>::difference_type count(InputIt first, InputIt last, const T& value){typename iterator_traits<InputIt>::difference_type ret =0;for(; first != last;++first){if(*first == value){ ret++;}}return ret;}
Second version
template<class InputIt, class UnaryPredicate>typename iterator_traits<InputIt>::difference_type count_if(InputIt first, InputIt last, UnaryPredicate p){typename iterator_traits<InputIt>::difference_type ret =0;for(; first != last;++first){if(p(*first)){ ret++;}}return ret;}

Exemple

Au code count utilise pour déterminer le nombre de nombres entiers dans un std::vector correspond à une valeur cible .

Original:

The following code uses count to determine how many integers in a std::vector match a target value.

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#include <algorithm>#include <iostream>#include <vector>   int main(){int data[]={1, 2, 3, 4, 4, 3, 7, 8, 9, 10};std::vector<int> v(data, data+10);   int target1 =3;int target2 =5;int num_items1 = std::count(v.begin(), v.end(), target1);int num_items2 = std::count(v.begin(), v.end(), target2);   std::cout<<"number: "<< target1 <<" count: "<< num_items1 <<'\n';std::cout<<"number: "<< target2 <<" count: "<< num_items2 <<'\n';}

Résultat :

number: 3 count: 2 number: 5 count: 0

Cet exemple utilise un expression lambda de compter des éléments divisible par 3 .

Original:

This example uses a expression lambda to count elements divisible by 3.

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#include <algorithm>#include <iostream>#include <vector>   int main(){int data[]={1, 2, 3, 4, 4, 3, 7, 8, 9, 10};std::vector<int> v(data, data+10);   int num_items1 = std::count_if(v.begin(), v.end(), [](int i){return i %3==0;});   std::cout<<"number divisible by three: "<< num_items1 <<'\n';}

Résultat :

number divisible by three: 3