使用int []运算符的3D数组C++

Question

我是C/C++的新手,我一直在讨厌,但仍然不知道如何制作这样的"结构"

它应该是一个使用指针的3D动态数组.

我这样开始,但卡在那里

  int x=5,y=4,z=3;
  int ***sec=new int **[x];

知道如何使其成为y和z的静态大小就足够了;

拜托,我很感激你的帮助.

提前致谢.

Answer 1

要动态创建3D整数数组,最好先了解1D和2D数组.

1D阵列:你可以很容易地做到这一点

const int MAX_SIZE=128;
int *arr1D = new int[MAX_SIZE];

在这里,我们创建一个int指针,指向可以存储整数的内存块.

2D数组:您可以使用上述1D数组的解来创建2D数组.首先,创建一个指向内存块的指针,其中只保存其他整数指针,最终指向实际数据.由于我们的第一个指针指向一个指针数组,所以这将被称为指针指针(双指针).

const int HEIGHT=20;
const int WIDTH=20;

int **arr2D = new int*[WIDTH];  //create an array of int pointers (int*), that will point to 
                                //data as described in 1D array.
for(int i = 0;i < WIDTH; i++){
      arr2D[i] = new int[HEIGHT]; 
}

3D阵列:这就是你想要做的.在这里,您可以尝试上述两种情况中使用的方案.应用与2D阵列相同的逻辑.有问题的图解释了所有.第一个数组将是指向指针的指针(int*** - 因为它指向双指针).解决方案如下:

const int X=20;
const int Y=20;
const int z=20;

int ***arr3D = new int**[X];
for(int i =0; i<X; i++){
   arr3D[i] = new int*[Y];
   for(int j =0; j<Y; j++){
       arr3D[i][j] = new int[Z];
       for(int k = 0; k<Z;k++){
          arr3D[i][j][k] = 0;
       }
   }
}

Answer 2

// one-liner
typedef std::vector<std::vector<std::vector<int> > > ThreeDimensions;
// expanded
typedef std::vector<int> OneDimension;
typedef std::vector<OneDimension> TwoDimensions;
typedef std::vector<TwoDimension> ThreeDimensions;

(毕竟这是标记的c ++)

编辑以回应乔的问题

你好再次乔=)肯定.这是一个例子:

#include <vector>
#include <iostream>

int main(int argc, char* const argv[]) {

    /* one-liner */
    typedef std::vector<std::vector<std::vector<int> > >ThreeDimensions;
    /* expanded */
    typedef std::vector<int>OneDimension;
    typedef std::vector<OneDimension>TwoDimensions;
    typedef std::vector<TwoDimensions>ThreeDimensions;

    /*
       create 3 * 10 * 25 array filled with '12'
     */
    const size_t NElements1(25);
    const size_t NElements2(10);
    const size_t NElements3(3);
    const int InitialValueForAllEntries(12);

    ThreeDimensions three_dim(NElements3, TwoDimensions(NElements2, OneDimension(NElements1, InitialValueForAllEntries)));

    /* the easiest way to assign a value is to use the subscript operator */
    three_dim[0][0][0] = 11;
    /* now read the value: */
    std::cout << "It should be 11: " << three_dim[0][0][0] << "\n";
    /* every other value should be 12: */
    std::cout << "It should be 12: " << three_dim[0][1][0] << "\n";

    /* get a reference to a 2d vector: */
    TwoDimensions& two_dim(three_dim[1]);

    /* assignment */
    two_dim[2][4] = -1;
    /* read it: */
    std::cout << "It should be -1: " << two_dim[2][4] << "\n";

    /* get a reference to a 1d vector: */
    OneDimension& one_dim(two_dim[2]);

    /* read it (this is two_dim[2][4], aka three_dim[1][2][4]): */
    std::cout << "It should be -1: " << one_dim[4] << "\n";
    /* you can also use at(size_t): */
    std::cout << "It should be 12: " << one_dim.at(5) << "\n";

    return 0;
}