Sudoku code checker in c [closed] - c

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I'm writing a Sudoku solution checker for a class and I've hit a wall.
I'm at the point where I'm checking if I can see whether or individual columns and rows are unique. For some reason the code works on 4x4 grids but as soon as I get up to a 5x5 grid or higher (goal is to get to a 9x9 grid) the program starts to print out that it had failed even when it should succeed.
Any help would be much needed, I want need a point in the right direction or where I should look into
Here's the code:
#include <stdio.h>
#include <stdlib.h>
int main ()
{
int i, j, n, k, p, q;
int fail;
int array[5][5];
int check[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
int a = 0;
char *output = NULL;
scanf("%d", &n);
// memory allocated for yes or no at end
output = malloc(sizeof(int) * (n));
while (a < n)
{
fail = 0;
// create this 2D array
for (i = 0; i < 5; i++)
{
for (j = 0; j < 5; j++)
{
scanf("%d", &(array[i][j]));
}
}
// seeing if row is unique
for (i = 0; i < 5; i++)
{
for (j = 0; j < 5; j++)
{
for (k = 0; k < 5; k++)
{
if (array[i][k] == array[i][k+1])
fail += 1;
}
}
}
// seeing if column is unique
for (i = 0; i < 5; i++)
{
for (j = 0; j < 5; j++)
{
for (k = 0; k < 5; k++)
{
if (array[k][j] == array[k+1][j])
fail += 1;
}
}
}
/* for (WHAT DO I DO FOR ROWS)
{
for (WHAT DO I DO FOR ROWS AGAIN BUT REPLACE ROWS WITH COLUMNS)
{
for (NOW IM LOST)
}
}
*/
// success or failure? 0 success, 1 failure
if (fail >= 1)
output[a] = 1;
else
output[a] = 0;
a++;
}
// print out yah or nah
for (i = 0; i < n; i++)
{
if (output[i] == 0)
printf("YES\n");
else
printf("NO\n");
}
return 0;
}
Forget my for loop for the grids, I'll work on that once I figure out how to get the columns and rows working correctly.
Thanks for the help!
Here is an input that would cause the program to fail when it should succeed
1
1 2 3 4 5
2 3 4 5 1
3 4 5 1 2
4 5 1 2 3
5 1 2 3 4
output would be
NO
EDIT: It is now working with a 9x9 grid! Thanks for the help!
#include <stdio.h>
#include <stdlib.h>
#define SIDE_LENGTH 9
int main ()
{
int i, j, n, k, p, q;
int fail;
int array[SIDE_LENGTH][SIDE_LENGTH];
int check[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
int a = 0;
char *output = NULL;
scanf("%d", &n);
// memory allocated for yes or no at end
output = malloc(sizeof(int) * (n));
while (a < n)
{
fail = 0;
// create this 2D array
for (i = 0; i < SIDE_LENGTH; i++)
{
for (j = 0; j < SIDE_LENGTH; j++)
{
scanf("%d", &(array[i][j]));
}
}
// seeing if row is unique
for (i = 0; i < SIDE_LENGTH; i++)
{
for (j = 0; j < SIDE_LENGTH; j++)
{
for (k = 0; k < SIDE_LENGTH - 1; k++)
{
if (array[i][k] == array[i][k+1])
fail += 1;
}
}
}
// seeing if column is unique
for (i = 0; i < SIDE_LENGTH; i++)
{
for (j = 0; j < SIDE_LENGTH; j++)
{
for (k = 0; k < SIDE_LENGTH - 1; k++)
{
if (array[k][j] == array[k+1][j])
fail += 1;
}
}
}
/* for (WHAT DO I DO FOR ROWS)
{
for (WHAT DO I DO FOR ROWS AGAIN BUT REPLACE ROWS WITH COLUMNS)
{
for (NOW IM LOST)
}
}
*/
// success or failure? 0 success, 1 failure
if (fail >= 1)
output[a] = 1;
else
output[a] = 0;
a++;
}
// print out yah or nah
for (i = 0; i < n; i++)
{
if (output[i] == 0)
printf("YES\n");
else
printf("NO\n");
}
return 0;
}
input:
1
1 2 3 4 5 6 7 8 9
2 3 4 5 6 7 8 9 1
3 4 5 6 7 8 9 1 2
4 5 6 7 8 9 1 2 3
5 6 7 8 9 1 2 3 4
6 7 8 9 1 2 3 4 5
7 8 9 1 2 3 4 5 6
8 9 1 2 3 4 5 6 7
9 1 2 3 4 5 6 7 8

Answer 1

#ameyCU helped find the error in my code
Setting k to one less than what i and j were set to allowed the code to successfully run on any X*X sized grid. Because k is one less than i and j, it won't try to access a part of the array that hasn't been allocated yet which is where my problem lied.

Answer 2

for (i = 0; i < 5; i++)
{
for (j = 0; j < 5; j++)
{
for (k = 0; k < 5; k++)
{
if (array[i][k] == array[i][k+1])
fail += 1;
}
}
}
Despite the overwriting of the array as already pointed out, your logic is flawed. You don't use j at all. You are just comparing the same values five times.

Answer 3

The problem is the comparison.
if (array[i][k] == array[i][k+1])
I think you are using i as row and column index, then using j to iterate for duplicates. k will be what you compare against so ...
/* compare if j'th value is same as k'th value */
if (j != k && array[i][j] == array[i][k]) /* Don't check same against same */
the second comparison should be
/* compare if j'th value is same as k'th value */
if (j != k && array[j][i] == array[k][i]) /* Don't check same against same */
That would fix your overflow (k+1) bug, and get you going.
The squares could be fixed with
struct co_ords {
int x;
int y;
};
struct co_ords boxes[][9] = {{ {0,0}, {0,1}, {0,2},
{1,0}, {1,1}, {1,2},
{2,0}, {2,1}, {2,2}
},
{ {3,0}, {3,1}, {3,2},
{4,0}, {4,1}, {4,2},
{5,0}, {5,1}, {5,2} },
... /* more boxes go here */
{ {6,6}, {6,7}, {6,8},
{7,6}, {7,7}, {7,8},
{8,6}, {8,7}, {8,8} }};
for( i = 0; i < 9; i++ ){
struct co_ords current_box * = boxes[i];
for( j = 0; j < 9; j++ ) {
for( k = 0; k < 9; k++ ){
if( j != k && array[ current_box[j].x ][ current_box[j].y] == array[ current_box[k].x ][ current_box[k].y] )
fail += 1;
}
}
}

Answer 4

int array[5][5];
so the array is allocated as 5x5
for (i = 0; i < 5; i++)
{
for (j = 0; j < 5; j++)
{
scanf("%d", &(array[i][j]));
}
}
and you are indexing from 0 to 5 ..
to use larger, please do replace all those "5"s with a precompiler definition.
#define SUDOKU_SIDE_LENGTH 5
...
int array[SUDOKU_SIDE_LENGTH ][SUDOKU_SIDE_LENGTH ];
...
for (i = 0; i < SUDOKU_SIDE_LENGTH ; i++)
{
for (j = 0; j < SUDOKU_SIDE_LENGTH ; j++)
{
scanf("%d", &(array[i][j]));
}
}
etc.. that will ensure that you always allocate enough space for the array.
adjust size on the definition, not in the code..