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std::partial_sum

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< cpp‎ | algorithm

 
 
アルゴリズムライブラリ
機能します
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Functions
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シーケンス動作を非改変
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Non-modifying sequence operations
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シーケンス動作を変更する
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Modifying sequence operations
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操作を仕切る
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Partitioning operations
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(ソートされた範囲で)ソート操作
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Sorting operations (on sorted ranges)
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バイナリ検索操作(ソート範囲で)
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Binary search operations (on sorted ranges)
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(ソートされた範囲で)操作を設定します
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Set operations (on sorted ranges)
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Heap operations
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最小値/最大値操作
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Minimum/maximum operations
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数値演算
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Numeric operations
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adjacent_difference
partial_sum
Cライブラリ
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C library
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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)
レンジ[first, last)の部分範囲内の要素の部分和を計算し、d_firstで範囲の先頭に書き込みます。最初のバージョンは、要素を総括するoperator+使用し、2番目のバージョンは、指定されたバイナリop機能を使用しています.
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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同等の操作:
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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);
...

目次

[編集] パラメータ

first, last -
和への要素の範囲
Original:
the range of elements to sum
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d_first -
目的の範囲の始まり
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.

[編集] 値を返します

書き込まれた最後の要素過去の要素を指すイテレータ.
Original:
Iterator to the element past the last element written.
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[編集] 複雑

二項演算の正確(last - first) - 1アプリケーション
Original:
Exactly (last - first) - 1 applications of the binary operation
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[編集] 可能な実装

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;
}

[編集]

#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

[編集] も参照してください

範囲内の隣接する要素間の差を計算します
Original:
computes the differences between adjacent elements in a range
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(関数テンプレート) [edit]
要素の範囲をまとめている
Original:
sums up a range of elements
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(関数テンプレート) [edit]