java - 计算不均匀二维数组中的列总和

Question

我一直在通过一些免费的在线教程自学 Java，并挑战自己完成几乎所有的练习。我已经在这个问题上坚持了一个星期了，这让我发疯。我觉得我已经相当接近了，只是被构成不均匀列的不同数组长度绊倒了。

            public class Testing {
                public static void main(String[] args) {
                    int[][] data = { {3, 2, 5},
                                     {1, 4, 4, 8, 13},
                                     {9, 1, 0, 2},
                                     {0, 2, 6, 3, -1, -8} };

                    int sum = 0;
                    int row = 0;
                    int col = 0;
                    int currentRow = 0;

                    while (currentRow < data.length) {
                        for (col = 0; col < data[currentRow].length; col++) {
                            sum = 0;
                            for (row = 0; row < data.length; row++) {
                                System.out.println(data[row][col]);
                                sum += data[row][col];
                            }
                            System.out.println("Sum: " + sum);
                        } 
                        currentRow++;
                    }   
                }
            }

Answer 1

如果您尝试计算行总和

似乎有一个循环太多了。您的 while 遍历第一个维度，而 for(row... 遍历第二个维度。因此，无需通过 for(row. ..尝试少用一个循环:

       public class Testing {
            public static void main(String[] args) {
                int[][] data = { {3, 2, 5},
                                 {1, 4, 4, 8, 13},
                                 {9, 1, 0, 2},
                                 {0, 2, 6, 3, -1, -8} };

                int sum = 0;

                for (int currentRow = 0; currentRow < data.length; currentRow++) {
                    sum = 0;
                    for (int col = 0; col < data[currentRow].length; col++) {
                        System.out.println(data[currentRow][col]);
                        sum += data[currentRow][col];
                    } 
                    System.out.println("Sum: " + sum);
                }   
            }
        }

如果您尝试计算列总和

public class Testing {
    public static void main(String[] args) {
        int[][] data = { {3, 2, 5},
                         {1, 4, 4, 8, 13},
                         {9, 1, 0, 2},
                         {0, 2, 6, 3, -1, -8} };
            // get max length of a row == number of columns
        int length = 0;
        for (int r = 0; r < data.length; r++) {
            int currLength = data[r].length;
            if(currLength>length) length = currLength;
        }
            // create array for column sums
        int[] sums = new int[length];
            // fill array with zeros
        Arrays.fill(sums, 0);
            // sum up
        for (int currentRow = 0; currentRow < data.length; currentRow++) {
            for (int col = 0; col < data[currentRow].length; col++) {
                System.out.println(data[currentRow][col]);
                sums[col] += data[currentRow][col];
            } 
        }   
            // print sums
        for (int i = 0; i < sums.length; i++) {
            System.out.println(i + ": " + sums[i]);
        }
    }
}