📜  C ++和Java的多维数组之间的区别

📅  最后修改于: 2021-05-31 19:15:57             🧑  作者: Mango

先决条件: C++中的多维数组, Java的多维数组

多维数组

多维数组是存储多个元素的数组的表格表示形式。这些维可以是一维数组,二维数组等。多维数组在C++和Java都可用,但是它们的实现和某些属性是不同的。

在C / C++中的实现

在C++中,多维数组在内部创建为巨型线性数组。 C++语法将该线性内存块抽象为2或3维行为,从而使程序员易于使用。

例子:

尺寸为2行x 3列{{9,45,51},{5,25,6}}的2D数组的实现如下(假设Integer占用4个字节):

因此,特定索引处的内部元素的内部公式为:

假设基址为3000 。然后arr [1] [1] = 3000 +(1 * 3 * 4)+ 1 * 4 = 3000 + 12 + 4 = 3016

由于这样的实现,每一行的列数必须相等,并且为了正确访问元素,在声明时必须指定列大小。

下面是C++中多维数组的实现:

C++
// C++ program for multidimention array
// implementation
#include 
using namespace std;
  
// Driver Code
int main()
{
    // Create a 2d integer array,
    // dimensions: 3rows X 5cols
    int arr[3][5] = {
        { 23, 56, 34, 52, 63 },
        { 40, 20, 96, 43, 97 },
        { 75, 51, 10, 82, 43 }
    };
  
    // Traversing of 2D array
    cout << "Printing entire 2d array: "
         << endl;
  
    // Iterate over the rows
    for (int i = 0; i < 3; i++) {
  
        // Iterate over the cols
        for (int j = 0; j < 5; j++) {
  
            cout << "arr[" << i << "][" << j
                 << "]:" << arr[i][j]
                 << "      ";
        }
        cout << endl;
    }
  
    return 0;
}


Java
// Java program for multidimensional
// array implementation
import java.io.*;
  
class GFG {
  
    // Driver Code
    public static void main(String[] args)
    {
  
        // Create a 2D integer array
        // dimensions: 3rows X 5cols
        int[][] arr = {
            { 23, 56, 34, 52, 63 },
            { 40, 20, 96, 43, 97 },
            { 75, 51, 10, 82, 43 }
        };
  
        // Traversing the 2D array
        System.out.println("Printing entire 2d array: ");
  
        // Iterate over the rows
        for (int i = 0;
             i < arr.length; i++) {
  
            // Iterate over the cols
            for (int j = 0;
                 j < arr[i].length; j++) {
                System.out.print(
                    "arr[" + i + "][" + j
                    + "]:" + arr[i][j]
                    + "    ");
            }
            System.out.println();
        }
        System.out.println();
  
        // Reassigning arr[2] to another
        // array
  
        // This is not possible in 2D
        // arrays in C++, instead of
        // there is array of pointers
        arr[2] = new int[] { 82, 53, 64,
                             12, 45, 3 };
  
        // Traversing the array again
        System.out.println(
            "Printing entire 2d array "
            + "afer modification: ");
  
        // Iterate over the rows
        for (int i = 0;
             i < arr.length; i++) {
  
            // Iterate over the cols
            for (int j = 0;
                 j < arr[i].length; j++) {
  
                System.out.print(
                    "arr[" + i + "][" + j
                    + "]:" + arr[i][j]
                    + "    ");
            }
            System.out.println();
        }
    }
}


输出:
Printing entire 2d array: 
arr[0][0]:23      arr[0][1]:56      arr[0][2]:34      arr[0][3]:52      arr[0][4]:63      
arr[1][0]:40      arr[1][1]:20      arr[1][2]:96      arr[1][3]:43      arr[1][4]:97      
arr[2][0]:75      arr[2][1]:51      arr[2][2]:10      arr[2][3]:82      arr[2][4]:43

用Java实现

在Java,多维数组被实现为数组的数组,其中基本数组的每个索引均指的是一个完全不同的数组。因此, arr [rowIndex]返回整个一维数组,而arr [rowIndex] [coLIndex]返回该一维数组中索引为coLIndex的元素。

例子:

以下是Java多维数组的实现:

Java

// Java program for multidimensional
// array implementation
import java.io.*;
  
class GFG {
  
    // Driver Code
    public static void main(String[] args)
    {
  
        // Create a 2D integer array
        // dimensions: 3rows X 5cols
        int[][] arr = {
            { 23, 56, 34, 52, 63 },
            { 40, 20, 96, 43, 97 },
            { 75, 51, 10, 82, 43 }
        };
  
        // Traversing the 2D array
        System.out.println("Printing entire 2d array: ");
  
        // Iterate over the rows
        for (int i = 0;
             i < arr.length; i++) {
  
            // Iterate over the cols
            for (int j = 0;
                 j < arr[i].length; j++) {
                System.out.print(
                    "arr[" + i + "][" + j
                    + "]:" + arr[i][j]
                    + "    ");
            }
            System.out.println();
        }
        System.out.println();
  
        // Reassigning arr[2] to another
        // array
  
        // This is not possible in 2D
        // arrays in C++, instead of
        // there is array of pointers
        arr[2] = new int[] { 82, 53, 64,
                             12, 45, 3 };
  
        // Traversing the array again
        System.out.println(
            "Printing entire 2d array "
            + "afer modification: ");
  
        // Iterate over the rows
        for (int i = 0;
             i < arr.length; i++) {
  
            // Iterate over the cols
            for (int j = 0;
                 j < arr[i].length; j++) {
  
                System.out.print(
                    "arr[" + i + "][" + j
                    + "]:" + arr[i][j]
                    + "    ");
            }
            System.out.println();
        }
    }
}
输出:
Printing entire 2d array: 
arr[0][0]:23    arr[0][1]:56    arr[0][2]:34    arr[0][3]:52    arr[0][4]:63    
arr[1][0]:40    arr[1][1]:20    arr[1][2]:96    arr[1][3]:43    arr[1][4]:97    
arr[2][0]:75    arr[2][1]:51    arr[2][2]:10    arr[2][3]:82    arr[2][4]:43    

Printing entire 2d array afer modification: 
arr[0][0]:23    arr[0][1]:56    arr[0][2]:34    arr[0][3]:52    arr[0][4]:63    
arr[1][0]:40    arr[1][1]:20    arr[1][2]:96    arr[1][3]:43    arr[1][4]:97    
arr[2][0]:82    arr[2][1]:53    arr[2][2]:64    arr[2][3]:12    arr[2][4]:45    arr[2][5]:3
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