C language wrong output...pascal triangle using 2d arrays - c

Question

So this is my code for printing pascal triangle using 2d arrays but its not giving me the desired output and I cannot determine what's wrong with the logic/code.
#include <stdio.h>
int main()
{
int num, rows, col, k;
printf("Enter the number of rows of pascal triangle you want:");
scanf("%d", &num);
long a[100][100];
for (rows = 0; rows < num; rows++)
{
for (col = 0; col < (num - rows - 1); col++)
printf(" ");
for (k = 0; k <= rows; k++)
{
if (k == 0 || k == rows)
{
a[rows][k] = 1;
printf("%ld", a[rows][k]);
}
else
a[rows][k] = (a[rows - 1][k - 1]) + (a[rows - 1][k]);
printf("%ld", a[rows][k]);
}
printf("\n");
}
return 0;
}

Answer 1

You don't have curly braces around the statements after the else, so it looks like you'll double-printf() when the condition of the if-statement is true.
I copied the source into codechef.com/ide and changed the io for num to be just assigned to 6 which produced the following output:
Enter the number of rows of pascal triangle you want:
11
1111
11211
113311
1146411
1151010511
It looks like your close, but you want 1, 11, 121, 1331 etc right?
Wraping the else case produced the following output:
if (k == 0 || k == rows)
{
a[rows][k] = 1;
printf("(%ld)", a[rows][k]);
}
else{// START OF BLOCK HERE
a[rows][k] = (a[rows - 1][k - 1]) + (a[rows - 1][k]);
printf("(%ld)", a[rows][k]);
}//END OF BLOCK HERE, NOTE THAT IT INCLUDES THE PRINT IN THE ELSE CASE NOW
OUTPUT:
Enter the number of rows of pascal triangle you want:
(1)
(1)(1)
(1)(2)(1)
(1)(3)(3)(1)
(1)(4)(6)(4)(1)
(1)(5)(10)(10)(5)(1)
But i added () to make it clearer to me. I also added a "/n" to the end of the first printf that asks for the value of num, so that the first line is on a new line.
printf("Enter the number of rows of pascal triangle you want:\n");

Answer 2

You can do that without using any arrays:
#include <stdlib.h>
#include <stdio.h>
int num_digits(int number)
{
int digits = 0;
while (number) {
number /= 10;
++digits;
}
return digits;
}
unsigned max_pascal_value(int row)
{
int result = 1;
for (int num = row, denom = 1; num > denom; --num, ++denom)
result = (int)(result * (double)num / denom );
return result;
}
int main()
{
printf("Enter the number of rows of pascals triangle you want: ");
int rows;
if (scanf("%d", &rows) != 1) {
fputs("Input error. Expected an integer :(\n\n", stderr);
return EXIT_FAILURE;
}
int max_digits = num_digits(max_pascal_value(rows));
for (int i = 0; i <= rows; ++i) {
for (int k = 0; k < (rows - i) * max_digits / 2; ++k)
putchar(' ');
int previous = 1;
printf("%*i ", max_digits, previous);
for (int num = i, denom = 1; num; --num, ++denom) {
previous = (int)(previous * (double)num / denom );
printf("%*i ", max_digits, previous);
}
putchar('\n');
}
}
Output:
Enter the number of rows of pascals triangle you want: 15
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1 6 15 20 15 6 1
1 7 21 35 35 21 7 1
1 8 28 56 70 56 28 8 1
1 9 36 84 126 126 84 36 9 1
1 10 45 120 210 252 210 120 45 10 1
1 11 55 165 330 462 462 330 165 55 11 1
1 12 66 220 495 792 924 792 495 220 66 12 1
1 13 78 286 715 1287 1716 1716 1287 715 286 78 13 1
1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1
1 15 105 455 1365 3003 5005 6435 6435 5005 3003 1365 455 105 15 1