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std::partial_sum

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C++
 
Biblioteca algoritmo
Funções
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Functions
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Não modificar operações de seqüência
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Non-modifying sequence operations
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Modificando operações de seqüência
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Modifying sequence operations
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Particionamento operações
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Partitioning operations
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Operações de classificação (em intervalos ordenados)
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Sorting operations (on sorted ranges)
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Binários operações de busca (em intervalos ordenados)
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Binary search operations (on sorted ranges)
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Definir operações (em intervalos ordenados)
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Set operations (on sorted ranges)
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Operações de pilha
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Heap operations
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Mínimo / máximo de operações
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Minimum/maximum operations
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Operações numéricas
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Numeric operations
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partial_sum
C biblioteca
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C library
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Definido no cabeçalho <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)
Calcula as somas parciais dos elementos no subranges do [first, last) alcance e grava-los para o início escala em d_first. A primeira versão utiliza operator+ para resumir os elementos, a segunda versão utiliza a função binária dada 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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Operação equivalente:
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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);
...

Índice

[editar] Parâmetros

first, last -
a gama de elementos a soma
Original:
the range of elements to sum
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d_first -
o início do intervalo de destino
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.

[editar] Valor de retorno

Iterador para o elemento passado o último elemento escrito.
Original:
Iterator to the element past the last element written.
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[editar] Complexidade

Exatamente (last - first) - 1 aplicações da operação binária
Original:
Exactly (last - first) - 1 applications of the binary operation
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[editar] Possível implementação

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;
}

[editar] Exemplo

#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';
}

Saída: 

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

[editar] Veja também
calcula as diferenças entre elementos adjacentes em forma de intervalo
Original:
computes the differences between adjacent elements in a range
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(modelo de função) [edit]
resume uma série de elementos
Original:
sums up a range of elements
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(modelo de função) [edit]
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