Thread: Two dimensional arrays

Hi there guys, im new to the forum.

Currently a first year programming student, and struggling on arrays as i missed a lecture. Here's what i need to do, and what ive done, before i hit my point of not knowing any more.

Im trying to write a program that will read this data into a 2 dimensional array (data is 1,2,3,4,5,6,7,8,9) so, i've used this

Code:

int arr[3][3]={
               {1,2,3},
               {4,5,6},
               {7,8,9}
               };

then ive used

Code:

int i,j;

	for (i=0;i<3;++i)
   {
   	for(j=0;j<3;++j)
   	printf("%d",arr[i][j]);
      	printf("\n");
   }

to make the program produce the data into a nicely formatted array

1 2 3
4 5 6
7 8 9

Which so far is correct, and working.
Now i need to have the add the value's within the columns, and have them output a lower total, and a side total. What i mean is,

Code:

1   2   3| 6   
4   5   6| 15
7   8   9| 24
==========
12  15  18

Im stumped as to how i do this, and my text book only tells me so much, please, i hope you can help me!

MANY THANKS,

Masschino

consider that a[i][j] in your code snippet is used to access each element of the array, and then consider that you can control the values of i and j to access any element you want.

it's simple after that. for instance, the sum of the first row:

sum = a[0][0] + a[0][1] + a[0][2];

and the second:

sum = a[1][0] + a[1][1] + a[1][2];

and the third:

sum = a[2][0] + a[2][1] + a[2][2];

etc. write out the code to sum each row and column correctly - you can access any element with [row][row-element], or, if you prefer [column-element][column]. you can write loops to factor out similar code. for instance, the code to sum each row is the same in each case, except that the first index in the array is changed (by that i mean this a[i][j] <-> i is the first index, j is the second index).

i understand what you're pointing out to me, many thanks.
Didnt know i could do, say, sum=i[1][2] and etc.

That said, im still struggling to find a way to put it all in correctly, where does everything go?

ie

Code:

sum=i[1][1]+i[2][1]+i[3][1];
      	printf("\n%d",&sum);

Had the above to work out the sum of 1,4,7 in the array, wont work . Invalid indirection apparently.

in reply to above post:

array access starts at 0, not 1. so the item at row 1, column 1 is:
a[1][1], and row 1, column 2 is: a[1][2]. etc. you're reading elements which don't exit (ie a[1][3])
----

fill out these functions:

int sumrow(int row) { return sum; }
int sumcolumn(int column) { return sum; }

then, use them in the appropriate places in your display loop. f'rinstance, modify:

printf("\n");

to read:

printf(" | %d\n", sumrow(i));

>void main()
Big no-no. main returns an integer by definition. And you really should use spaces instead of tabs so that the formatting of your code isn't ruined when you post.