以相反的顺序将一个向量复制到另一个向量

Question

I am new in C++.
I need to copy a vector in reverse order to another vector.

Here's how i did it :

int temp[] = {3, 12, 17};

vector<int>v(temp, temp+3);

vector<int>n_v;

n_v=v;
reverse(n_v.begin(), n_v.end()); //Reversing new vector

Is there any simple way to copy a vector in reverse order to another vector in STL?

Answer 1

只需这样做：

vector<int>n_v (v.rbegin(), v.rend());

Answer 2

您可以使用reverse_iterator ：

std::vector<int> n_v(v.rbegin(), v.rend());

Answer 3

From C++20, the views can be used.

std::vector v = { 1,2,3,4,5,6,7,8 };
auto result = v | std::views::reverse ;

Here the result can be directly iterated 8 7 6 5 4 3 2 1 .

But if still need a vector

std::vector rev_v(std::ranges::begin(result), std::ranges::end(result));

The advantage of these viewer adapters is, we can chain up multiple requirements.

For example, if the requirement says, reverse the vector, get the first four squaring them. We can do this in one statement.

auto result = v | std::views::reverse | std::views::take(4) | std::views::transform([](int i) { return i * i; });

The output is 64 49 36 25