The most common kind of multidimensional array is the two-dimensional array. If you think of a one-dimensional array as a column of values, you can think of a two-dimensional array as a table of values like this
c0 |
c1 |
c2 |
c3 |
|
r0 |
0 |
1 |
2 |
3 |
r1 |
1 |
2 |
3 |
4 |
r2 |
2 |
3 |
4 |
5 |
r3 |
3 |
4 |
5 |
6 |
r4 |
4 |
5 |
6 |
7 |
Here we have an array with five rows and four columns. It has twenty total elements. However we say it has dimension five by four, not dimension twenty. This array is not the same as a four by five array like this one:
c0 |
c1 |
c2 |
c3 |
c4 |
|
r0 |
0 |
1 |
2 |
3 |
4 |
r1 |
1 |
2 |
3 |
4 |
5 |
r2 |
2 |
3 |
4 |
5 |
6 |
r3 |
3 |
4 |
5 |
6 |
7 |
We need to use two numbers to identify a position in a two-dimensional array.
These are the element's row and column positions. For instance if the above array
is called J
then J[0][0]
is 0, J[0][1]
is 1, J[0][2]
is 2, J[0][3]
is 3, J[1][0]
is 1,
and so on.
Here's how the elements in a four by five array called M
are referred to:
M[0][0] | M[0][1] | M[0][2] | M[0][3] | M[0][4] |
M[1][0] | M[1][1] | M[1][2] | M[1][3] | M[1][4] |
M[2][0] | M[2][1] | M[2][2] | M[2][3] | M[2][4] |
M[3][0] | M[3][1] | M[3][2] | M[3][3] | M[3][4] |