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std::partial_sum

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< cpp‎ | algorithm

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C++
 
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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Opérations numériques
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Numeric operations
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adjacent_difference
partial_sum
Bibliothèque C
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C library
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Déclaré dans l'en-tête <numeric>
template< class InputIt, class OutputIt >
OutputIt partial_sum( InputIt first, InputIt last, OutputIt d_first );
 (1)
template< class InputIt, class OutputIt, class BinaryOperation >

OutputIt partial_sum( InputIt first, InputIt last, OutputIt d_first,

                      BinaryOperation op );
 (2)
Calcule les sommes partielles des éléments de la sous-gammes de [first, last) gamme et les écrit dans le début de la plage à d_first. La première version utilise operator+ de résumer les éléments, la deuxième version utilise la fonction binaire donné op .
Original:
Computes the partial sums of the elements in the subranges of the range [first, last) and writes them to the range beginning at d_first. The first version uses operator+ to sum up the elements, the second version uses the given binary function op.
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Opération équivalente:
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Equivalent operation:
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*(d_first)   = *first;
*(d_first+1) = *first + *(first+1);
*(d_first+2) = *first + *(first+1) + *(first+2);
*(d_first+3) = *first + *(first+1) + *(first+2) + *(first+3);
...

Sommaire

[modifier] Paramètres

first, last -
la gamme des éléments de somme
Original:
the range of elements to sum
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d_first -
le début de la plage de destination
Original:
the beginning of the destination range
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op - binary operation function object that will be applied.

The signature of the function should be equivalent to the following:

 Ret fun(const Type1 &a, const Type2 &b);

The signature does not need to have const &.
The type  Type1 must be such that an object of type iterator_traits<InputIt>::value_type can be implicitly converted to  Type1. The type  Type2 must be such that an object of type InputIt can be dereferenced and then implicitly converted to  Type2. The type  Ret must be such that an object of type iterator_traits<InputIt>::value_type can be assigned a value of type  Ret. ​

Type requirements
-
InputIt must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

[modifier] Retourne la valeur

Itérateur à l'élément après le dernier élément écrit .
Original:
Iterator to the element past the last element written.
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[modifier] Complexité

Exactement (last - first) - 1 applications de l'opération binaire
Original:
Exactly (last - first) - 1 applications of the binary operation
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[modifier] Mise en œuvre possible

First version 
template<class InputIt, class OutputIt>
OutputIt partial_sum(InputIt first, InputIt last, 
                           OutputIt d_first)
{
    return std::partial_sum(first, last, d_first, 
                            std::plus<InputIt, InputIt>());
}
Second version 
template<class InputIt, class OutputIt, class BinaryOperator>
OutputIt partial_sum(InputIt first, InputIt last, 
                           OutputIt d_first, BinaryOperation op)
{
    if (first == last) return d_first;
 
    typename std::iterator_traits<InputIt>::value_type sum = *first;
    *d_first = sum;
 
    while (++first != last) {
       sum = op(sum, *first);
       *++d_first = sum;
    }
    return ++d_first;
}

[modifier] Exemple

#include <numeric>
#include <vector>
#include <iostream>
#include <iterator>
#include <functional>
int main()
{
    std::vector<int> v = {2,2,2,2,2,2,2,2,2,2};
 
    std::cout << "The first 10 even numbers are: ";
    std::partial_sum(v.begin(), v.end(), 
                     std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
 
    std::partial_sum(v.begin(), v.end(), v.begin(), std::multiplies<int>());
    std::cout << "The first 10 powers of 2 are: ";
    for(auto n: v) {
        std::cout << n << " ";
    }
    std::cout << '\n';
}

Résultat : 

The first 10 even numbers are: 2 4 6 8 10 12 14 16 18 20 
The first 10 powers of 2 are: 2 4 8 16 32 64 128 256 512 1024

[modifier] Voir aussi
calcule les différences entre les éléments adjacents dans une gamme
Original:
computes the differences between adjacent elements in a range
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(fonction générique) [edit]
résume un ensemble d'éléments
Original:
sums up a range of elements
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(fonction générique) [edit]
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