Pascal's triangle in C weird output

Question

I'm trying to write a program to display Pascal's triangle up to a user-inputted number of levels. We aren't allowed to use the factorial method. My current code is this:

#include <stdio.h>

void trianglePrint(const int numLevels);

int main() {
  int numLevels;

  printf("Please enter how many levels of Pascal's Triangle you would 
  like to see: ");
  scanf("%d", &numLevels);

  trianglePrint(numLevels);


  return 0;
}

void trianglePrint(const int numLevels) {
  int pascalTriangle[28][28];
  int i, j;

  for (i = 0; i < numLevels; ++i) {
    for (j = 0; j <= i; ++j) {
      if (i == 0 || i == 1 || j == 0 || j == numLevels) {
        pascalTriangle[i][j] = 1;
        printf("%d ", pascalTriangle[i][j]);
      }
      else {
        pascalTriangle[i][j] = pascalTriangle[i - 1][j - 1] + 
        pascalTriangle[i - 1][j];
        printf("%d ", pascalTriangle[i][j]);
      }
    }
    printf("\n");
  }

}

We're only supposed to be able to go up to 28 levels, which is why I am using an array of size 28 in both dimensions.
This works fine for about 6 levels of the triangle, but for larger levels it gives really large integers. I assumed it was due to uninitialized arrays, but I'm not sure. Does anyone know where the error is?

Answer 1

If you change

if (i == 0 || i == 1 || j == 0 || j == numLevels)

to

if (i == 0 || i == 1 || j == 0 || j == i)

(thanks to Melpomene), then all accesses to your array end up on already intiailised members.

That solves the strange numbers.

Output:

Please enter how many levels of Pascal's Triangle you would like to see: 6
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1

Process returned 0 (0x0)   execution time : 2.264 s
Press any key to continue.

Note:
Also initialising an array is a wise precaution. You could initialise with values which help finding an error, instead of hiding it, e.g. 42.