我想创建一个双精度向量的向量，并希望它已经具有 (32,32,16) 个元素，而无需手动将所有这些推回。有没有办法在初始化期间做到这一点？（我不在乎推动什么价值）。
我想要一个 3 维数组，第一个维度有 32 个，第二个维度有 32 个，第三个维度有 16 个元素。
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4 回答
8
一个班轮：
std::vector< std::vector< std::vector<double> > > values(32, std::vector< std::vector<double> >(32, std::vector<double>(16, 0.0)));
或打破界限：
typedef std::vector<double> v_type;
typedef std::vector<v_type> vv_type;
typedef std::vector<vv_type> vvv_type;
vvv_type values(32, vv_type(32, v_type(16, 0.0)));
我会说这分配了很多对象（32 * 32 * 16）。
单个向量会起作用吗？
std::vector<double> values(32*32*16, 0.0)
那将是 32*32*16-1 少new。
于 2010-06-08T15:24:24.827 回答
3
向量的一个 ctor 允许您指定要复制到向量元素中的大小和值。我不太确定“（32,32,16）”元素是什么意思，但是您可以执行以下操作：
// create a vector containing 16 elements set to 2
std::vector<int> temp(16, 2);
// create a vector of 32 vectors, each with 16 elements set to 2
std::vector<std::vector<int> > values(32, temp);
于 2010-06-08T15:17:39.600 回答
2
干得好：
vector<vector<vector<int> > > k(32, vector<vector<int> >(32, vector<int>(16,0)));
我什至不会问为什么你会想要这样一个怪物，而不是仅仅使用一个vector带有你自己的索引方案的单个。
于 2010-06-08T15:22:55.190 回答
0
由于事先知道大小，并且您需要将整个数组转换为一维数组（对于 OpenGL），为什么不为它创建一个类呢？我创建了一个基于模板的 3D 数组实现，希望对您有用。
用法：
typedef Array3D<double, 3, 3, 3> DoubleArray333;
DoubleArray333 array;
Double val = 0.0;
for (size_t i = 0; i < DoubleArray333::SizeX; ++i)
{
for (size_t j = 0; j < DoubleArray333::SizeY; ++j)
{
for (size_t k = 0; k < DoubleArray333::SizeZ; ++k)
{
array(i, j, k) = val++;
}
}
}
for (size_t i = 0; i < DoubleArray333::ArraySize; ++i)
{
std::cout<<array[i]<<" ";
}
Array3D 头文件：
#pragma once
#include <exception>
#include <sstream>
#include <utility>
#include <memory>
/**
* \brief A 3D array of variable type and size.
* \author Vite Falcon
* \date 08/06/2010
**/
template <typename T, int x, int y, int z>
class Array3D
{
private:
T* m_array;
/**
* \brief Validate the index range of different dimensions.
* \remarks Vite Falcon, 08/06/2010.
* \author Vite Falcon
* \date 08/06/2010
* \exception std::out_of_range Thrown when one of the indices is out-of-range.
* \param x The width index.
* \param y The height index.
* \param z The depth index.
**/
inline void validateRange(size_t x, size_t y, size_t z)
{
if (x >= SizeX || y >= SizeY || z >= SizeZ)
{
std::stringstream ss;
ss<<"Index out of range when accessing ("<<x<<", "<<y<<", "<<z<<
") when total size is ("<<SizeX<<", "<<SizeY<<", "<<SizeZ<<").";
throw std::out_of_range(ss.str());
}
}
/**
* \brief Validates the given array index.
* \remarks Vite Falcon, 08/06/2010.
* \author Vite Falcon
* \date 08/06/2010
* \exception std::out_of_range Thrown when the index is out-of-range.
* \param index Zero-based index of the array.
**/
inline void validateIndex(size_t index)
{
if (index >= ArraySize)
{
std::stringstream ss;
ss<<"Index out of range when accessing array by index "<<index<<
" when total array size is "<<ArraySize<<".";
throw std::out_of_range(ss.str());
}
}
public:
static const size_t SizeX;
static const size_t SizeY;
static const size_t SizeZ;
static const size_t ArraySize;
typedef Array3D<T,x,y,z> MyType;
/**
* \brief Default constructor.
* \author Vite Falcon
* \date 08/06/2010
**/
Array3D(void)
:m_array(new T[ArraySize])
{
}
/**
* \brief Copy constructor.
* \author Vite Falcon
* \date 08/06/2010
* \param other The other.
**/
Array3D(const MyType& other)
:m_array(new T[ArraySize])
{
memcpy_s(m_array, sizeof(T)*ArraySize, other.m_array, sizeof(T)*ArraySize);
}
/**
* \brief Destructor.
* \author Vite Falcon
* \date 08/06/2010
**/
~Array3D(void)
{
delete[] m_array;
m_array = 0;
}
/**
* \brief Gets the value at a particular array index.
* \author Vite Falcon
* \date 08/06/2010
* \param array_index Zero-based index of the array.
* \return The value at the given index.
**/
inline T& at(size_t array_index)
{
return (*this)[array_index];
}
/**
* \brief Gets the value at a particular array index (const version)
* \author Vite Falcon
* \date 08/06/2010
* \param array_index Zero-based index of the array.
* \return The value at the given index.
**/
inline const T& at(size_t array_index) const
{
return (*this)[array_index];
}
/**
* \brief Gets the value in the array from the given 3D indices.
* \author Vite Falcon
* \date 08/06/2010
* \param x The width index.
* \param y The height index.
* \param z The depth index.
* \return The value at the given indices.
**/
inline T& at(size_t x, size_t y, size_t z)
{
return (*this)(x, y, z);
}
/**
* \brief Gets the value in the array from the given 3D indices (const version).
* \author Vite Falcon
* \date 08/06/2010
* \param x The width index.
* \param y The height index.
* \param z The depth index.
* \return The value at the given indices.
**/
inline const T& at(size_t x, size_t y, size_t z) const
{
return (*this)(x, y, z);
}
/**
* \brief The '()' operator to access the values as a 3D array.
* \author Vite Falcon
* \date 08/06/2010
* \return The value at the given indices.
*
* \param x The width index.
* \param y The height index.
* \param z The depth index.
**/
inline T& operator ()(size_t x, size_t y, size_t z)
{
validateRange(x, y, z);
return m_array[x*SizeY*SizeZ + y*SizeZ + z];
}
/**
* \brief The '()' operator to access the values as a 3D array (const version).
* \author Vite Falcon
* \date 08/06/2010
* \return The value at the given indices.
*
* \param x The width index.
* \param y The height index.
* \param z The depth index.
**/
inline const T& operator()(size_t x, size_t y, size_t z) const
{
validateRange(x, y, z);
return m_array[x*SizeY*SizeZ + y*SizeZ + z];
}
/**
* \brief The '[]' operator to access the values as a 1D array.
* \author Vite Falcon
* \date 08/06/2010
* \param array_index Zero-based index of the array.
* \return Value at the given index.
**/
inline T& operator[](size_t array_index)
{
validateIndex(array_index);
return m_array[array_index];
}
/**
* \brief The '[]' operator to access the values as a 1D array.
* \author Vite Falcon
* \date 08/06/2010
* \param array_index Zero-based index of the array.
* \return Value at the given index.
**/
inline const T& operator[](size_t array_index) const
{
validateIndex(array_index);
return m_array[array_index];
}
/**
* \brief Fills the array with the given value.
* \author Vite Falcon
* \date 08/06/2010
* \param val The value to fill the array.
**/
void fill(const T& val)
{
for (size_t i = 0; i < ArraySize; ++i)
{
m_array[i] = val;
}
}
/**
* \brief Gets the raw array.
* \author Vite Falcon
* \date 08/06/2010
* \return The 1D array.
**/
T* getArray()
{
return m_array;
}
/**
* \brief Swaps the current array with the given one.
* \author Vite Falcon
* \date 08/06/2010
* \param [in,out] other The other.
**/
void swap(MyType& other)
{
std::swap(m_array, other.m_array);
}
/**
* \brief Copy operator.
* \author Vite Falcon
* \date 08/06/2010
* \param other The other.
* \return A shallow copy of this object.
**/
MyType& operator = (const MyType& other)
{
MyType temp(other);
swap(temp);
return *this;
}
};
template <typename T, int x, int y, int z>
const size_t Array3D<T, x, y, z>::SizeX = x;
template <typename T, int x, int y, int z>
const size_t Array3D<T, x, y, z>::SizeY = y;
template <typename T, int x, int y, int z>
const size_t Array3D<T, x, y, z>::SizeZ = z;
template <typename T, int x, int y, int z>
const size_t Array3D<T, x, y, z>::ArraySize = x*y*z;
您还可以使用以下函数将指向数组的指针作为一维数组：double* double_array = array.getArray();
编辑：更改用法以使用 double 而不是 int 显示它。
于 2010-06-08T21:07:42.147 回答