Array fills nice but read out gives problems

[lamko]

I've written a function who fills the array with the numbers 1 to 9. It's a 8 puzzle game. First I fill the array for the winning numbers. And in the second for loop I'll compare the values from the existing board to the winning board. But the moment I read out the winning board I expect a 3 but get a 4.

bool
won(void)
{

    int count = 0;
    int winboard[d][d];
    int inc = 1;
    int swap = 0;
    int k = 0;
    int l = 0;
    for (i = 0 ; i <= d -1 ; i++)
    {
        for (j = 0 ; j <= d -1; j++)
        {
            winboard[i][j] = inc++;

            printf("test %d\n", winboard[i][j]);
        }
    }
    // init winning board and compare to current board
    for (i = 0 ; i <= d -1 ; i++)
    {
        for (j = 0 ; j <= d -1; j++)
        {
            k= winboard[i][j];
            printf("%d\n", k);
            l= board[i][j];
            //printf("%d\n", l);
            if(winboard[i][j] == board[i][j])
                count++;
            if (count == (d*d)-1)
                return true;

        }

    }
    return false;
}

Here the output from the program :

test 1
test 2
test 3
test 4
test 5
test 6
test 7
test 8
test 9
1
2
4
4
5
7
7
8
9

You ll see nicely filled but the read out ??

[tabstop]

If your arrays are of size d-1 as you say, then your loops go way too far.

[CommonTater]

Where does your d variable come from?
You can't just make them up and use them without initialization...

Even if d is correctly initialized you are using it incorrectly...

int winboard[d-1][d-1];  // your board is now one too small

for (i = 0 ; i <= d -1 ; i++)  // and what is this about?

Your for() loop is going to overflow your array boundaries.

I'm thinking you need to re-read the section on arrays in your tutorial/textbook...

[AndrewHunter]

As tabstop said:

bool
won(void)
{

    int count = 0;
    int winboard[d-1][d-1];
    int inc = 1;
    int swap = 0;
    int k = 0;
    int l = 0;
    for (i = 0 ; i <= d -1 ; i++)
    {
        for (j = 0 ; j <= d -1; j++)

In C arrays begin at zero. Can you see your problem?

[stahta01]

You are running past the array bounds.

int winboard[d-1][d-1];

The smallest is winboard[0][0] the largest is winboard[d-2][d-2]

You are using winboard[d-1][d-1] which does not exist.

Tim S.

[lamko]

d i'll put in as program argument which is between min val 3 and max val 9. I'm not totally understanding what you mean by overflowing the array. I'm going to check that out.
d are the dimensions of the array if I want an 8 puzzle. I'll input a 3 but arrays start at zero so it would correct it to start at 1.
This is the winning board:

0,0 0,1 0,2
1,0 1,1 1,2
2,0 2,1 2,2

1 2 3
4 5 6
7 8 0

Now the intialising board

8 7 6
5 4 3
2 1 0

[kpark91]

d i'll put in as program argument which is between min val 3 and max val 9. I'm not totally understanding what you mean by overflowing the array. I'm going to check that out.

It means even tho you declare it as

int windboard[2] //2 elements in windboard[]

you will only have index of 0 and 1 in the array.
meaning that calling windboard[2] would be out of bounds.

So, array index starts from 0 and ends at n - 1 when you have declared it like int a[n]

[lamko]

You are running past the array bounds.

int winboard[d-1][d-1];

The smallest is winboard[0][0] the largest is winboard[d-2][d-2]

You are using winboard[d-1][d-1] which does not exist.

Tim S.

If I fill in for d = 3
winboard[2][2] as max size

So I don't understand how do you come at winboard[d-2][d-2] as max size ??

[AndrewHunter]

Lesson 8 - Arrays.

[lamko]

It means even tho you declare it as

int windboard[2] //2 elements in windboard[]

you will only have index of 0 and 1 in the array.
meaning that calling windboard[2] would be out of bounds.

So, array index starts from 0 and ends at n - 1 when you have declared it like int a[n]

I thought with winboard[2] you get 3 elements

I'll get it now I just should use d as array size that is what you mean.

If updated the code in the starting post. I'll read some more on array because it's not exactly working with winboard[d][d]

[CommonTater]

I thought with winboard[2] you get 3 elements

Think about this rationally... why on earth would asking for 2 elements get you 3?
When you ask for 2 elements you get 2 elements... numbered 0 and 1 ...

I'll get it now I just should use d as array size that is what you mean.

There are more problems than that...
You are overrunning the array bounds with every for() loop...

Here... type this example up, run it and watch what comes out of it...

#include <stdio.h>
#define SIZE 4

int main (void)
  {
     int matrix[SIZE][SIZE];   // 4 x 4 element 2 dimensional array...
     int xpos,ypos;      // x and y matrix positions

     // fill the array with numbers
     for (xpos = 0; xpos < SIZE; xpos++)
       for (ypos = 0; ypos < SIZE; ypos++)
           matrix[xpos][ypos] = xpos * ypos;

     // display array content
     for (xpos = 0; xpos < SIZE; xpos++)
       for (ypos = 0; ypos < SIZE; ypos++)
           printf("matrix[%d][%d] = %d\n",xpos,ypos,matrix[xpos][ypos]);

   return 0; }

[AndrewHunter]

I thought with winboard[2] you get 3 elements

No, you get exactly what you ask for in C. You asked for an array of 2 ints. Their indexes are 0 and 1.

I'll read some more on array because it's not exactly working with winboard[d][d]

Sounds like a good idea. Look at the link I posted.

[lamko]

I've changed both nested for loops now to this :
for (i = 0 ; i < d ; i++)
for (j = 0 ; j < d; j++)

It's working fine now.
thx to all especially CommonTater for his example which made al clear !