横向二维锯齿阵列，列优先

Question

Given a 2D array named testing . I know how to transverse a jagged array, but it would start testing[0][0] and then go to testing[0][1] .

How would I transverse this jagged array starting at [0][0] and then going to [1][0] ?

Here is what I have tried thus far...

        for (int x = 0, counter = 0; x < testing[counter].length; x++) {
            for (int y = 0; y < testing.length; y++) {
                System.out.println(testing[y][x]);
        }

        counter++;
    }
}

Answer 1

The problem with iterating a jagged array on the inner index first, is knowing when to stop (that is the outer loop invariant) and knowing to skip processing the inner loop entirely (that is a break condition).

To get the outer loop invariant, you could use a couple of different approaches. One simple way would be to compute the max inner index ahead of time. A more efficient approach would be a do-while loop. It checks a did-I-do-any-work boolean at the end of the loop, and continues if so. That way you don't have to precompute the max inner index.

To get the break condition, just check length of the array stored in the second dimension.