std::rotate_copy

template <class ForwardIterator, class OutputIterator>  OutputIterator rotate_copy (ForwardIterator first, ForwardIterator middle,                              ForwardIterator last, OutputIterator result);

Copy range rotated left

Copies the elements in the range [first,last) to the range beginning at result, but rotating the order of the elements in such a way that the element pointed by middle becomes the first element in the resulting range.

此函数模板的行为等同于

template <class ForwardIterator, class OutputIterator>
  OutputIterator rotate_copy (ForwardIterator first, ForwardIterator middle,
                              ForwardIterator last, OutputIterator result)
{
  result=std::copy (middle,last,result);
  return std::copy (first,middle,result);
}

参数

first, last: Forward iterators to the initial and final positions of the range to be copy-rotated. The range used is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
Notice that in this function, these are not consecutive parameters, but the first and third ones.
middle: Forward iterator pointing to the element within the range [first,last) that is copied as the first element in the resulting range.
result: Output iterator to the initial position of the range where the reversed range is stored.
The pointed type shall support being assigned the value of an element in the range [first,last).

这些范围不应重叠。

返回值

An output iterator pointing to the end of the copied range.

示例

// rotate_copy algorithm example
#include <iostream>     // std::cout
#include <algorithm>    // std::rotate_copy
#include <vector>       // std::vector

int main () {
  int myints[] = {10,20,30,40,50,60,70};

  std::vector<int> myvector (7);

  std::rotate_copy(myints,myints+3,myints+7,myvector.begin());

  // print out content:
  std::cout << "myvector contains:";
  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    std::cout << ' ' << *it;
  std::cout << '\n';

  return 0;
}

输出

myvector contains: 40 50 60 70 10 20 30

复杂度

Linear in the distance between first and last: Performs an assignment for each element.

数据竞争

访问范围 [first,last) 中的对象。
修改 result 和返回的迭代器之间的范围内的对象。
Each object is accessed exactly once.

异常

Throws if either an element assignment or an operation on an iterator throws.
请注意，无效参数会导致未定义行为。

另见

rotate: 将范围中的元素向左旋转（函数模板）

reverse_copy: 复制并反转范围（函数模板）

random_shuffle: 随机重排范围中的元素（函数模板）

copy: 复制元素范围（函数模板）