java - 如何计算不规则二维数组的列长度？

Question

我想计算二维数组中行和列的长度。我知道如何执行行部分，但是我不知道如何找到此数组中列的长度。

public class array2D {
    public static void main(String args[]) {
        int maxNumberOfColumns = 8;
        Integer[][] j = {
                {2, 4, 8, 5, 1, 3, 7, 2},
                {6, 7, 4, 8, 2},
                {2, 3, 5, 9, 7, 1}};

        for (int row = 0; row < j.length; row++) {
            for (int col = 0; col < j[row].length; col++) {
                System.out.print(j[row][col] + "  ");
            }
            System.out.println();
        }

        System.out.println();
        System.out.println("------------");
        System.out.println();

        for (int row = 0; row < j.length; row++) {
            System.out.println("row "+row+" has "+j[row].length+" elements");
        }
        System.out.println();

        for (int col = 0; col < maxNumberOfColumns; col++) {
            //code I don't know
        }
    }
}

Answer 1

您可以将最后一个 for 循环更改为下面的内容以打印每列的计数。我在这里使用内部循环来计算元素数量

for (int col = 0; col < maxNumberOfColumns; col++) {
    int count = 0;
    for (int i = 0; i < j.length; i++) {
        if (j[i].length > col) {
            count++;
        }
    }
    System.out.println("Column " + (col + 1) + " has " + count + " elements");
}

另一种解决方案是使用

计算第一个循环中的最小列数

minNumberOfColumns = length < minNumberOfColumns ? length : minNumberOfColumns;

然后将最后一个循环更改为

System.out.println("Column 1 to " + minNumberOfColumns + " has " + j.length + " elements");
for (int col = minNumberOfColumns; col < maxNumberOfColumns; col++) {
    int count = 0;
    for (int i = 0; i < j.length; i++) {
        if (j[i].length > col) {
            count++;
        }
    }
    System.out.println("Column " + (col + 1) + " has " + count + " elements");
}