Java中的锯齿状数组

先决条件： Java中的数组

锯齿状数组是数组的数组，其成员数组可以有不同的大小，也就是说，我们可以创建一个二维数组，但每行的列数是可变的。这些类型的数组也称为锯齿状数组。

内存中锯齿状数组的图示：

锯齿状数组

锯齿状数组的声明和初始化：

Syntax: data_type array_name[][] = new data_type[n][];  //n: no. of rows
             array_name[] = new data_type[n1] //n1= no. of columns in row-1
             array_name[] = new data_type[n2] //n2= no. of columns in row-2
             array_name[] = new data_type[n3] //n3= no. of columns in row-3
                                   .
                                   .
                                   .
             array_name[] = new data_type[nk]  //nk=no. of columns in row-n

另一种初始化锯齿状数组的方法：

int arr_name[][] = new int[][]  {
                                  new int[] {10, 20, 30 ,40},
                                  new int[] {50, 60, 70, 80, 90, 100},
                                  new int[] {110, 120}
                                      };
                                      
                              OR                                     
                                                         
                    int[][] arr_name = {
                          new int[] {10, 20, 30 ,40},
                          new int[] {50, 60, 70, 80, 90, 100},
                          new int[] {110, 120}
                              };
                              
                              OR                                     
                                                         
                    int[][] arr_name = {
                           {10, 20, 30 ,40},
                           {50, 60, 70, 80, 90, 100},
                           {110, 120}
                              };

以下是演示上述概念的Java程序。

Java

// Program to demonstrate 2-D jagged array in Java
class Main {
    public static void main(String[] args)
    {
        // Declaring 2-D array with 2 rows
        int arr[][] = new int[2][];
 
        // Making the above array Jagged
 
        // First row has 3 columns
        arr[0] = new int[3];
 
        // Second row has 2 columns
        arr[1] = new int[2];
 
        // Initializing array
        int count = 0;
        for (int i = 0; i < arr.length; i++)
            for (int j = 0; j < arr[i].length; j++)
                arr[i][j] = count++;
 
        // Displaying the values of 2D Jagged array
        System.out.println("Contents of 2D Jagged Array");
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++)
                System.out.print(arr[i][j] + " ");
            System.out.println();
        }
    }
}

输出

Contents of 2D Jagged Array
0 1 2 
3 4 

以下是第 i 行有 i 列的另一个示例，即第一行有 1 个元素，第二行有两个元素，依此类推。

Java

// Another Java program to demonstrate 2-D jagged
// array such that first row has 1 element, second
// row has two elements and so on.
class Main {
    public static void main(String[] args)
    {
        int r = 5;
 
        // Declaring 2-D array with 5 rows
        int arr[][] = new int[r][];
 
        // Creating a 2D array such that first row
        // has 1 element, second row has two
        // elements and so on.
        for (int i = 0; i < arr.length; i++)
            arr[i] = new int[i + 1];
 
        // Initializing array
        int count = 0;
        for (int i = 0; i < arr.length; i++)
            for (int j = 0; j < arr[i].length; j++)
                arr[i][j] = count++;
 
        // Displaying the values of 2D Jagged array
        System.out.println("Contents of 2D Jagged Array");
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++)
                System.out.print(arr[i][j] + " ");
            System.out.println();
        }
    }
}

输出

Contents of 2D Jagged Array
0 
1 2 
3 4 5 
6 7 8 9 
10 11 12 13 14