Fill 2d array in spiral order in c - c

Question

I'm doing program where I enter the number from keyboard. Then 2d array is created, and it's filled in spiral order till this number. All elements after the number will be equal to 0; The function fills the array in spiral order (to right -> down -> left -> up).
Code is:
#include <stdio.h>
#include <time.h>
void spiral(int array[100][100], int m, int n, int s)
{
int size, b, x = 0, y = 1, num = 1;
size = m*n;
for (num=1;num<=size+1;num++)
{
for (b = x; b < n; b++)
{
if (num <=s) {
array[x][b] = num;
num++;
}
else array[x][b] = 0;
}
if (num == size + 1)
{
break;
}
for (b = y; b < m; b++)
{
if (num <=s) {
array[b][n - 1] = num;
num++;
}
else array[b][n - 1] = 0;
}
if (num == size + 1)
{
break;
}
y++;
n--;
for (b = n - 1; b > x; b--)
{
if (num <= s) {
array[m - 1][b] = num;
num++;
}
else array[m - 1][b] = 0;
}
if (num == size + 1)
{
break;
}
for (b = m - 1; b > x; b--)
{
if (num <= s) {
array[b][x] = num;
num++;
}
else array[b][x] = 0;
}
x++;
m--;
}
}
int main()
{
int m, n, s, array[100][100];
srand(time(NULL));
//m=3;
// n=4;
m = 2 + rand() % 5;
n = 2 + rand() % 5;
//memset(array, 0, sizeof(array[0][0]) * 10 * 10);
printf("enter the number \n");
scanf("%i", &s);
spiral(array, m, n, s);
for (int i = 0; i < m; i++)
{
for (int j = 0; j < n; j++)
{
printf("%i\t", array[i][j]);
}
printf("\n");
}
return (0); }
However it doesn't work always correctly.
For example when i enter 15 and the program generates 4*3 array the output is`
1 2 3
10 12 4
9 -858993460 5
8 7 6`
However expected output is
1 2 3
10 11 4
9 12 5
8 7 6
Or when i enter 15 and the program generates 4*5 array the output is
1 2 3 4 5
14 0 0 0 6
13 0 0 0 7
12 11 10 9 8
And the expected output is
1 2 3 4 5
14 15 0 0 6
13 0 0 0 7
12 11 10 9 8
I can't find whats wrong with this code.

Answer 1

Try this:
void printArray(int array[10][10], int m, int n) {
for (int i = 0; i < m; i++)
{
for (int j = 0; j < n; j++)
{
printf("%i\t", array[i][j]);
}
printf("\n");
}
printf("\n");
}
void spiral(int array[10][10], int m, int n, int s)
{
int size, b, x = 0, y = 1, num = 1;
size = m*n;
while ( num <= s )
{
for (b = x; b < n; b++)
{
if (num <= s) {
array[x][b] = num;
num++;
} else array[x][b] = 0;
}
if (num == size + 1)
{
break;
}
for (b = y; b < m; b++)
{
if (num <= s) {
array[b][n - 1] = num;
num++;
} else array[b][n - 1] = 0;
}
if (num == size + 1)
{
break;
}
y++;
n--;
for (b = n - 1; b > x; b--)
{
if (num <= s) {
array[m - 1][b] = num;
num++;
} else array[m - 1][b] = 0;
}
if (num == size + 1)
{
break;
}
for (b = m - 1; b > x; b--)
{
if (num <= s) {
array[b][x] = num;
num++;
} else array[b][x] = 0;
}
x++;
m--;
}
}
int main()
{
int m, n, s, array[10][10];
srand(time(NULL));
m = 2 + rand() % 5;
n = 2 + rand() % 5;
memset(array, 0, sizeof(array[0][0]) * 10* 10);
printf("enter the number \n");
scanf("%i", &s);
spiral(array, m, n, s);
printArray(array, m, n);
return (0);
}
Before you had some weird for loop on top of your spiral function. The num++ in it interfered with the fact that you already increased num by one and made it skip the number the next time it would write in the uppermost line.
I changed it to a while loop that runs until num>s and it seems to work for me now.
Note that I just added printArray for easier debugging.