How do you count the position in an array?

Question

Label the elements in a 2D array by counting left to right across each row, and starting with the top row, working your way down. For the example above, we'd label each element like so:
0 1 2 3
4 5 6 7
8 9 10 11
12 13 14 15
16 17 18 19
Such labels give the position in the linearized array (so called because we can store them in a one-dimensional array now). (We did this secretely when we constructed deck out of suit and rank. Check out pages 91�92 if you need to refresh your memory.)
Come up with a way to calculate the row of an element in the two-dimensional array given its linearized position. For example, the row of element 6 is 1. Also devise a way to calculate the column of a element in the two-dimensional array given its position in the linearized array. For example, the column of element 6 is 2. (Remember, we start counting at zero.) Explain how you arrived at your answer.
There is no code needed for this, and my question is how should I start this? I am not sure how to track down a value in a two dimensional array... can anyone help?

Answer 1

Java arrays can be "ragged". Assuming the outer array represents rows and the inner array represents columns, the inner arrays that define the columns can be of different length. In your example you could have
0 1 2
3 4 5 6 7 8
9 10 11 12 13 14
15
16 17 18 19
So. unless you can specify that the column arrays will all be the same size, you'll have to have some way of determining the array size before it can be use in any calculation. You will find <anArray>length useful.