C++数组声明的方式

指针数组：array of pointers，即用于存储指针的数组，也就是数组元素都是指针

数组指针：a pointer to an array，即指向数组的指针

还要注意的是他们用法的区别，下面举例说明。

int* a[4] 指针数组

表示：数组a中的元素都为int型指针

元素表示：*a[i]   *(a[i])是一样的，因为[]优先级高于*

int (*a)[4] 数组指针

表示：指向数组a的指针
元素表示：(*a)[i]

3维

第一种：

dynamic_array.h

#ifndef DYNAMICARRAY_H
#define DYNAMICARRAY_H

class DynamicArray
{
public:
DynamicArray();
double*** allocate3DoubleArray(int x, int y, int z);
void release3DoubleArray(double*** the_array, int x, int y, int z);
};

#endif // DYNAMICARRAY_H

dynamic_array.cpp

#include "dynamic_array.h"

DynamicArray::DynamicArray()
{

}

double*** DynamicArray::allocate3DoubleArray(int x, int y, int z)
{
double*** the_array = new double**[x];
for(int i(0); i < x; i++)
{
the_array[i] = new double*[y];

for(int j(0); j < y; j++)
{
the_array[i][j] = new double[z];

for(int k(0); k < z; k++)
{
the_array[i][j][k]= 0.;
}
}
}
return the_array;
}

void DynamicArray::release3DoubleArray(double*** the_array, int x, int y, int z)
{
for (int i = 0; i < x; i++)
{
for (int j = 0; j < y; j++)
{
delete [] the_array[i][j];
}
delete [] the_array[i];
}
delete [] the_array;
}

第二种

float(*a)[100][100]=new float [100][100][100];

delete [] a;

第三种也是目前比较常用的一种：智能指针。

见：/article/10626331.html

vector 数组

#include <iostream>
#include <vector>
int main()
{
std::vector< std::vector<int> > v(100, std::vector<int>(100));
v[99][99] = 7;
std::cout << v[99][99] << '\n';
}

#include <iostream>
#include <memory>

struct Vec3
{
int x, y, z;
Vec3() : x(0), y(0), z(0) { }
Vec3(int x, int y, int z) :x(x), y(y), z(z) { }
friend std::ostream& operator<<(std::ostream& os, Vec3& v) {
return os << '{' << "x:" << v.x << " y:" << v.y << " z:" << v.z  << '}';
}
};

int main()
{
// Use the default constructor.
std::unique_ptr<Vec3> v1(new Vec3);
// Use the constructor that matches these arguments
std::unique_ptr<Vec3> v2(new Vec3(0, 1, 2));
// Create a unique_ptr to an array of 5 elements
std::unique_ptr<Vec3[]> v3(new Vec3[5]);

std::cout << "make_unique<Vec3>():      " << *v1 << '\n'
<< "make_unique<Vec3>(0,1,2): " << *v2 << '\n'
<< "make_unique<Vec3[]>(5):   " << '\n';
for (int i = 0; i < 5; i++) {
std::cout << "     " << v3[i] << '\n';
}
}

array

#include <iostream>
#include <array>
using namespace std;

int main ()
{
//--这是1维数组
array<float,5> a1={1,2,3,4,5};
cout <<"a1="<<endl;
for (size_t n=0; n<a1.size(); n++){
cout << a1
<<'\t';
}
cout << endl;
//当然也可以使用
cout <<"a1="<<endl;
for (size_t n=0; n<a1.size(); n++){
cout << a1.at(n) << '\t';
}
cout << endl;
//-----------------------------------------------
//--这是2维数组,共3行2列
array<array<float,2>,3 > a2={1.1,2,3,4,5,6};
//-----------------------------------------------
cout <<"a2="<<endl;
for (size_t m=0; m<a2.size(); m++){
for (size_t n=0; n<a2[m].size(); n++){
cout << a2[m]
<<'\t';
}
cout << endl;
}
//-----------------------------------------------

return 0;
}