std::adjacent_difference - cppreference.com

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Definido no cabeçalho `<numeric>`

`template< class InputIt, class OutputIt > OutputIt adjacent_difference( InputIt first, InputIt last, OutputIt d_first );`	(1)

`template< class InputIt, class OutputIt, class BinaryOperation > OutputIt adjacent_difference( InputIt first, InputIt last, OutputIt d_first, BinaryOperation op );`	(2)

Calcula as diferenças entre a segunda e a primeira de cada par adjacente de elementos da gama [first, last) e grava-os da gama de d_first + 1. Cópia sem modificações de first é escrito para d_first. A primeira versão utiliza operator- para calcular as diferenças, a segunda versão utiliza a função binária dada op.

Original:

Computes the differences between the second and the first of each adjacent pair of elements of the range [first, last) and writes them to the range beginning at d_first + 1. Unmodified copy of first is written to d_first. The first version uses operator- to calculate the differences, the second version uses the given binary function op.

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Operação equivalente:

Original:

Equivalent operation:

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*(d_first)   = *first;
*(d_first+1) = (*first+1) - *(first);
*(d_first+2) = (*first+2) - *(first+1);
*(d_first+3) = (*first+3) - *(first+2);
...

Parâmetros

first, last	-	o intervalo de elementos Original: the 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.
d_first	-	o início do intervalo de destino 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 types `Type1` and `Type2` must be such that an object of type `iterator_traits<InputIt>::value_type` can be implicitly converted to both of them. The type `Ret` must be such that an object of type `OutputIt` can be dereferenced and assigned a value of type `Ret`.
Type requirements
-`InputIt` must meet the requirements of `InputIterator`.
-`OutputIt` must meet the requirements of `OutputIterator`.

Valor de retorno

Ao elemento passado o último elemento escrito.

Original:

It to the element past the last element written.

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Complexidade

Exatamente (last - first) - 1 aplicações da operação binária

Original:

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

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Possível implementação

First version
template<class InputIt, class OutputIt> OutputIt adjacent_difference(InputIt first, InputIt last, OutputIt d_first) { if (first == last) return d_first; typedef typename std::iterator_traits<InputIt>::value_type value_t; value_t acc = first; d_first = acc; while (++first != last) { value_t val = first; ++d_first = val - acc; acc = std::move(val); } return ++d_first; }
Second version
template<class InputIt, class T, class BinaryOperation> OutputIt adjacent_difference(InputIt first, InputIt last, OutputIt d_first, BinaryOperation op) { if (first == last) return d_first; typedef typename std::iterator_traits<InputIt>::value_type value_t; value_t acc = first; d_first = acc; while (++first != last) { value_t val = first; ++d_first = op(val, acc); acc = std::move(val); } return ++d_first; }

First version

template<class InputIt, class OutputIt>
OutputIt adjacent_difference(InputIt first, InputIt last, 
                             OutputIt d_first)
{
    if (first == last) return d_first;

    typedef typename std::iterator_traits<InputIt>::value_type value_t;
    value_t acc = *first;
    *d_first = acc;
    while (++first != last) {
        value_t val = *first;
        *++d_first = val - acc;
        acc = std::move(val);
    }
    return ++d_first;
}

Second version

template<class InputIt, class T, class BinaryOperation>
OutputIt adjacent_difference(InputIt first, InputIt last, 
                             OutputIt d_first, BinaryOperation op)
{
    if (first == last) return d_first;

    typedef typename std::iterator_traits<InputIt>::value_type value_t;
    value_t acc = *first;
    *d_first = acc;
    while (++first != last) {
        value_t val = *first;
        *++d_first = op(val, acc);
        acc = std::move(val);
    }
    return ++d_first;
}

Exemplo

O código a seguir converte uma seqüência de números pares de repetições do número 2 e converte uma seqüência de uns a uma seqüência de números de Fibonacci .

Original:

The following code converts a sequence of even numbers to repetitions of the number 2 and converts a sequence of ones to a sequence of Fibonacci numbers.

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#include <numeric>
#include <vector>
#include <iostream>
#include <functional>
int main()
{
    std::vector<int> v{2, 4, 6, 8, 10, 12, 14, 16, 18, 20};
    std::adjacent_difference(v.begin(), v.end(), v.begin());
 
    for(auto n: v) {
        std::cout << n << ' ';
    }
    std::cout << '\n';

    v = {1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
    std::adjacent_difference(v.begin(), v.end()-1, v.begin()+1, std::plus<int>()

    for(auto n: v) {
        std::cout << n << ' ';
    }
    std::cout << '\n';
}

Saída:

2 2 2 2 2 2 2 2 2 2
1 1 2 3 5 8 13 21 34 55

Veja também


	calcula a soma parcial de um conjunto de elementos Original: computes the partial sum of 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. (modelo de função) [edit]

	resume uma série de elementos 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. (modelo de função) [edit]