如何在C++中动态分配3D数组

先决条件：数组基础
在C / C++中，简单单词中的多维数组作为数组的数组。多维数组中的数据以表格形式(以行主顺序)存储。以下是声明N维数组的一般形式：

多维数组的语法：

data_type  array_name[size1][size2]….[sizeN];

data_type: Type of data to be stored in the array. 
Here data_type is valid C/C++ data type
array_name: Name of the array
size1, size2, …, sizeN: Sizes of the dimensions

3-D数组是二维数组的数组：

3D数组的语法：

data_type array_name[x][y][z];
data_type: Type of data to be stored. Valid C/C++ data type.

有关多维和3D数组的更多详细信息，请参阅C++中的多维数组文章。

问题：给定3D数组，任务是使用C++中的new为3D数组动态分配内存。

解决方案：在以下方法中，使用的方法是制作两个2-D数组，每个2-D数组具有3行和4列，并具有以下值。

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16
17 18 19 20
21 22 23 24

X = No of 2D arrays.
Y = No of rows of each 2D array.
Z = No of columns of each 2D array.

方法1：使用单个指针–在这种方法中，分配了一个大小为x * y * z的存储块，然后使用指针算法访问这些存储块。以下是相同的程序：

C++

// C++ program to dynamically allocate
// the memory for 3D array in C++
// using new operator
#include 
using namespace std;
 
// Driver Code
int main()
{
    // Dimensions of the 3D array
    int x = 2, y = 3, z = 4;
    int count = 0;
 
    // Allocate memory blocks
    // of size x*y*z
    int* a = new int[x * y * z];
 
    // Traverse the 3D array
    for (int i = 0; i < x; i++) {
        for (int j = 0; j < y; j++) {
            for (int k = 0; k < z; k++) {
 
                // Assign values to the
                // memory blocks created
                *(a + i * y * z + j * z + k) = ++count;
            }
        }
    }
 
    // Traverse the 3D array again
    for (int i = 0; i < x; i++) {
        for (int j = 0; j < y; j++) {
            for (int k = 0; k < z; k++) {
 
                // Print values of the
                // memory blocks created
                cout << *(a + i * y * z + j * z + k) << " ";
            }
            cout << endl;
        }
        cout << endl;
    }
 
    // Deallocate memory
    delete[] a;
 
    return 0;
}

输出：

1 2 3 4 
5 6 7 8 
9 10 11 12 

13 14 15 16 
17 18 19 20 
21 22 23 24

方法2：使用三重指针–下图说明了该概念：

以下是相同的程序：

C++

// C++ program to dynamically allocate
// the memory for 3D array in C++
// using new operator
#include 
using namespace std;
 
// Driver Code
int main()
{
     
    // Dimensions of the 3D array
    int x = 2, y = 3, z = 4;
    int count = 0;
 
    // Allocate memory blocks of size
    // x i.e., no of 2D Arrays
    int*** a = new int**[x];
 
    for (int i = 0; i < x; i++) {
 
        // Allocate memory blocks for
        // rows of each 2D array
        a[i] = new int*[y];
 
        for (int j = 0; j < y; j++) {
 
            // Allocate memory blocks for
            // columns of each 2D array
            a[i][j] = new int[z];
        }
    }
 
    for (int i = 0; i < x; i++) {
        for (int j = 0; j < y; j++) {
            for (int k = 0; k < z; k++) {
 
                // Assign values to the
                // memory blocks created
                a[i][j][k] = ++count;
            }
        }
    }
 
    for (int i = 0; i < x; i++) {
        for (int j = 0; j < y; j++) {
            for (int k = 0; k < z; k++) {
 
                // Print values of the
                // memory blocks created
                cout << a[i][j][k] << " ";
            }
            cout << endl;
        }
        cout << endl;
    }
 
    // Deallocate memory
    for (int i = 0; i < x; i++) {
        for (int j = 0; j < y; j++) {
            delete[] a[i][j];
        }
        delete[] a[i];
    }
    delete[] a;
 
    return 0;
}

输出：

1 2 3 4 
5 6 7 8 
9 10 11 12 

13 14 15 16 
17 18 19 20 
21 22 23 24

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