“移动”两个向量在一起 [英] "move" two vectors together

问题描述

如果我有两个向量，并希望将它们合并到一个向量，我可以这样做：

If I have two vectors and want to combine them to one, I can do it the following way:

std::vector<T> a(100); // just some random size here
std::vector<T> b(100);

a.insert(std::end(a), std::begin(b), std::end(b));

这涉及到复制，我想避免。有什么办法使用移动语义来获得它们吗？

我非常怀疑它，因为向量应该是连续的。但是有任何方法可以用 deque

That involves copying though, which I want to avoid. Is there any way to use move-semantics to get them together?
I highly doubt it, as a vector is supposed to be contiguous. However is there any way to do it with a deque?

推荐答案

是，使用 std :: move ：

#include <algorithm>
std::move(b.begin(), b.end(), std::back_inserter(a));

或者，您可以使用move iterators：

Alternatively, you can use move iterators:

a.insert(a.end(),
         std::make_move_iterator(b.begin()), std::make_move_iterator(b.end()));

请记住 #include< iterator> 在这两种情况下，在开始之前，请说：

Remember to #include <iterator> in both cases, and before you begin, say:

a.reserve(a.size() + b.size());

根据值初始化的成本，与检查和增加大小计数器相比，以下变体可能也很有趣：

Depending on the cost of value-initialization compared to checking and incrementing the size counter, the following variant may also be interesting:

std::size_t n = a.size();
a.resize(a.size() + b.size());
std::move(b.begin(), b.end(), a.begin() + n);

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