C ++,copy设置为向量 [英] C++, copy set to vector
问题描述
我需要将 std :: set
复制到 std :: vector
:
std::set <double> input;
input.insert(5);
input.insert(6);
std::vector <double> output;
std::copy(input.begin(), input.end(), output.begin()); //Error: Vector iterator not dereferencable
问题在哪里?
推荐答案
您需要使用 back_inserter
:
std::copy(input.begin(), input.end(), std::back_inserter(output));
std :: copy
元素到你要插入的容器:它不能;它只有一个迭代器到容器中。因此,如果您将输出迭代器直接传递到 std :: copy
,您必须确保它指向一个范围,该范围至少足够大以容纳输入范围。
std::copy
doesn't add elements to the container into which you are inserting: it can't; it only has an iterator into the container. Because of this, if you pass an output iterator directly to std::copy
, you must make sure it points to a range that is at least large enough to hold the input range.
std :: back_inserter
创建一个输出迭代器,调用 push_back
在每个元素的容器上,因此每个元素都被插入到容器中。或者,您可以在 std :: vector
中创建足够数量的元素以保存要复制的范围:
std::back_inserter
creates an output iterator that calls push_back
on a container for each element, so each element is inserted into the container. Alternatively, you could have created a sufficient number of elements in the std::vector
to hold the range being copied:
std::vector<double> output(input.size());
std::copy(input.begin(), input.end(), output.begin());
或者,您可以使用 std :: vector
range constructor:
Or, you could use the std::vector
range constructor:
std::vector<double> output(input.begin(), input.end());
这篇关于C ++,copy设置为向量的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!