java - 如何计算二维数组中每一列的总和？

Question

我正在编写一个程序，以便它计算并打印数组每列的总和。给定的数据如下所示:

int[][] data = {{3, 2, 5},
                {1, 4, 4, 8, 13},
                {9, 1, 0, 2},
                {0, 2, 6, 3, -1, -8}};

理想情况下，它应该输出结果 13, 9, 15, 13, 12, -8。但由于某些行的长度不同，当我运行程序时，它输出 13, 9, 15 并给我一个 ArrayIndexOutOfBoundsException。而且我真的不知道如何解决它。

这是我的代码:

public class ColumnSums
{
public static void main(String[] args) {

    //The given data
    int[][] data = {{3, 2, 5},
                    {1, 4, 4, 8, 13},
                    {9, 1, 0, 2},
                    {0, 2, 6, 3, -1, -8}};

    //Determine the number of data in the longest row
    int LongestRow = 0;
    for ( int row=0; row < data.length; row++){
        if ( data[row].length > LongestRow ){
            LongestRow = data[row].length;
        }
    }
    System.out.println("The longest row in the array contains " + LongestRow + " values"); //Testing

    //Save each row's length into a new array (columnTotal)
    int[] columnTotal = new int[4];

    //Scan through the original data again
    //Record each row's length into a new array (columnTotal)
    System.out.println("The lengths of each row are: ");
    for ( int i = 0; i < data.length; i++){
        columnTotal[i] = data[i].length;
        System.out.println(columnTotal[i]); //Testing
    }


    // Create an array to store all the sums of column
    int ColumnSums[] = new int[LongestRow];
    System.out.println("The sums of each column are: ");

    for ( int i = 0; i < LongestRow; i++ ){

            int sum = 0;

            for (int j = 0; j < data.length; j++) {
                    sum = sum + data[j][i];
            }

            ColumnSums[i] = sum;
            System.out.println("Column " + i + ": " + ColumnSums[i]); //Testing
    }


}
}

感谢您的宝贵时间!!!

Answer 1

您基本上只需要循环遍历列，直到每行的计数器超出范围。无需提前循环查找最长的行。

   public static ArrayList<Integer> getCollumnSum() {
        int[][] data = {{3, 2, 5},
                        {1, 4, 4, 8, 13},
                        {9, 1, 0, 2},
                        {0, 2, 6, 3, -1, -8}};
        int col = 0;
        ArrayList<Integer> totals = new ArrayList<Integer>();
        while (true) {
          int total = 0;
          boolean dataInCol = false;
          for (int i = 0; i < data.length; i++) {
            if (col < data[i].length) {
                total += data[i][col];
                dataInCol = true;
            }
          }
          col += 1;
          if (dataInCol) {
            totals.add(total);
          } else {
            break;
          }
        }
        return totals;
      }

输出:

[13, 9, 15, 13, 12, -8]