Question

Possible Duplicate:
How do I use arrays in C++?

In the following code snippet:

int a[2][3][2]={{{1,2},{9,8},{3,7}},{{2,2},{1,4},{5,4}}};

what will be the answers for a[i],a[i][j] ,where i<=1 and j<=2
I have no problem in understanding the a[i][j][k] working.Can you please explain how does the above indexing works?

Answer 1

The thing you have to remember here is that the there are 2 different objects you are working with.

a[i][j][k]

and

a[i][j], a[i] and a

The first is an int, the other 3 are pointers

The associated memory’s look like this:

a       : | a[0] | a[1]|
             \/     \______________________
a[]     : | a[0][0] | a[0][1] | a[0][2] | a[1][0] | a[1][1] | a[1][2] |
             \/         \______________
a[][]   : | a[0][0][0] | a[0][0][1] | a[0][1][0] | a[0][1][1] | ...

And so on…

Now in the example you make you do arithmic operations with pointers eg. a[1] - a[0] = 3. If you look at the memory associated wit that you can see there are 3 memory locations between the 2 pointers, thus the result is 3.