std::partial_sum

 

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功能 Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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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
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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
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is_sorted （C++11） is_sorted_until （C++11） sort	partial_sort partial_sort_copy stable_sort nth_element
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Defined in header <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)

计算的部分和的范围[first, last)子范围中的元素，并且将它们写入到的范围内开始，d_first。使用operator+总结的第一个版本，第二个版本使用给定的二进制功能的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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相同的操作

Original:

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);
...

参数

first, last	-	元素的范围总和 Original: the range of elements to sum The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
d_first	-	的目标范围的开头 Original: the beginning of the destination range The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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.

返回值

迭代器写入过去的最后一个元素的元素.

Original:

Iterator to the element past the last element written.

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复杂性

究竟(last - first) - 1应用程序的二进制运算

Original:

Exactly (last - first) - 1 applications of the binary operation

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可能的实现

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; }

为例

#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';
}

Output:

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

另请参阅

adjacent_difference	计算的范围内的相邻元件之间的差异 Original: computes the differences between adjacent elements in a range The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函数模板）
accumulate	总结了一系列的元素 Original: sums up a range of elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （函数模板）