[英]Convert std::array<std::array<T,N>> into std::vector<T> in modern C++
I have a buch of triangles represented by a vector of 3d vectors ( std::vector<Vector3>
) and indices, represented in the following way 我有一个由3d向量( std::vector<Vector3>
)和索引的向量表示的三角形,用以下方式表示
using int3 = std::array<int, 3>;
std::vector<int3> indices;
I need to convert the indices
into a std::vector<size_t>
format to interact with a library. 我需要将indices
转换为std::vector<size_t>
格式以与库进行交互。
I know how to do this using raw loops, but I would like to here about how to do it using algorithms. 我知道如何使用原始循环执行此操作,但是我想在这里了解如何使用算法执行此操作。 I tried something like 我尝试了类似的东西
std::vector<size_t> indices_converted;
std::transform(std::begin(indices), std::end(indices), std::back_inserter(indices_converted), [](const auto &v) {
});
but is not enough, since I can't insert three values at once into the indices_converted
vector. 但这还不够,因为我无法一次将三个值插入indices_converted
向量。
So, what are your ideas? 那么,您有什么想法?
One-liner using latest version of range-v3 library: 一线使用最新版本的range-v3库:
#include <array>
#include <vector>
#include <range/v3/view/join.hpp>
#include <range/v3/range/conversion.hpp>
// ...
std::vector<std::array<int, 3>> v = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
const auto result = ranges::views::join(v) | ranges::to<std::vector>();
You can use either the range-based for loop or the standard algorithm std::for_each
. 您可以使用基于范围的for循环或标准算法std::for_each
。
For example 例如
#include <iostream>
#include <array>
#include <vector>
#include <iterator>
int main()
{
using int3 = std::array<int, 3>;
std::vector<int3> indices =
{
{ 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 }
};
std::vector<size_t> indices_converted;
indices_converted.reserve( 3 * indices.size() );
for ( const auto &item : indices )
{
indices_converted.insert( std::end( indices_converted ), std::begin( item ), std::end( item ) );
}
for ( const auto &item : indices_converted ) std::cout << item << ' ';
std::cout << '\n';
return 0;
}
or 要么
#include <iostream>
#include <array>
#include <vector>
#include <iterator>
#include <algorithm>
int main()
{
using int3 = std::array<int, 3>;
std::vector<int3> indices =
{
{ 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 }
};
std::vector<size_t> indices_converted;
indices_converted.reserve( 3 * indices.size() );
std::for_each( std::begin( indices ), std::end( indices ),
[&indices_converted]( const auto &item )
{
indices_converted.insert( std::end( indices_converted ), std::begin( item ), std::end( item ) );
} );
for ( const auto &item : indices_converted ) std::cout << item << ' ';
std::cout << '\n';
return 0;
}
In the both cases the output is 在这两种情况下,输出为
1 2 3 4 5 6 7 8 9
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.