Namespace
Varianti

std::accumulate

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< cpp‎ | algorithm

 
 
Algoritmo libreria
Funzioni
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Functions
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Non modifica le operazioni di sequenza
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Non-modifying sequence operations
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Modifica delle operazioni di sequenza
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Modifying sequence operations
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Partizionamento operazioni
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Partitioning operations
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Ordinamento delle operazioni (su intervalli ordinati)
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Sorting operations (on sorted ranges)
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Binarie (le operazioni di ricerca sui campi ordinati)
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Binary search operations (on sorted ranges)
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Impostare le operazioni (su intervalli ordinati)
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Set operations (on sorted ranges)
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Heap operazioni
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Heap operations
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Minimo / massimo le operazioni
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Minimum/maximum operations
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Operazioni numeriche
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Numeric operations
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iota(C++11)
accumulate
inner_product
Libreria C
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C library
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Defined in header <numeric>
template< class InputIt, class T >
T accumulate( InputIt first, InputIt last, T init );
(1)
template< class InputIt, class T, class BinaryOperation >

T accumulate( InputIt first, InputIt last, T init,

              BinaryOperation op );
(2)

Computes the sum of the given value init and the elements in the range [first, last). The first version uses operator+ to sum up the elements, the second version uses the given binary function op.

Indice

[modifica] Parametri

first, last -
l'intervallo di elementi di somma
Original:
the range of elements to sum
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init - initial value of the sum
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 T 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 T can be assigned a value of type  Ret. ​

Type requirements
-
InputIt must meet the requirements of InputIterator.
-
T must meet the requirements of CopyAssignable and CopyConstructible.

[modifica] Valore di ritorno

The sum of the given value and elements in the given range.

[modifica] Possibile implementazione

First version
template<class InputIt, class T>
T accumulate(InputIt first, InputIt last, T value)
{
    for (; first != last; ++first) {
        value = value + *first;
    }
    return value;
}
Second version
template<class InputIt, class T, class BinaryOperation>
T accumulate(InputIt first, InputIt last, T value, 
             BinaryOperation op)
{
    for (; first != last; ++first) {
        value = op(value, *first);
    }
    return value;
}

[modifica] Esempio

#include <iostream>
#include <vector>
#include <numeric>
#include <string>
 
int multiply(int x, int y)
{
    return x*y;
}
 
std::string magic_function(std::string res, int x)
{
    return res += (x > 5) ? "b" : "s";
}
 
int main()
{
    std::vector<int> v{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
 
    int sum = std::accumulate(v.begin(), v.end(), 0);
    int product = std::accumulate(v.begin(), v.end(), 1, multiply);
    std::string magic = std::accumulate(v.begin(), v.end(), std::string(), 
                                        magic_function);
 
    std::cout << sum << '\n'
              << product << '\n'
              << magic << '\n';
}

Output:

55
3628800
sssssbbbbb

[modifica] Vedi anche

calcola le differenze tra elementi adiacenti in un intervallo
Original:
computes the differences between adjacent elements in a range
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(funzione di modello) [edit]
calcola il prodotto interno di due gamme di elementi
Original:
computes the inner product of two ranges of elements
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(funzione di modello) [edit]
calcola la somma parziale di una serie di elementi
Original:
computes the partial sum of a range of elements
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(funzione di modello) [edit]