Why getting "Segmentation fault" for the dynamically allocated 2-D array?

Question

I am trying to generate pascal triangle by using the 2-d array which is dynamically allocated. But when I tried to run, its giving me "Segmentation Fault" error. What I am doing wrong in the code ?

int ** generate(int A, int *number_of_rows) {

     *number_of_rows = A;
     int **result = (int **)malloc(A * sizeof(int *));
     int i,j;
     for(i=0; i < A; i++){
         for(j=0; j<= i; j++){
             if(i==j || j==0)
                result[i][j] = 1;
             else
                result[i][j] = result[i-1][j] + result[i-1][j-1];
         }
     }
     return result;


}

Someone say I need to allocate memory for each row like below

for (i = 0; i < A; i++) 
        result[i] = (int *)malloc(i * sizeof(int));

but after doing that the function returns [0 ] [1 ] [2 ] [3 ] [4 ] instead of [1 ] [1 1 ] [1 2 1 ] [1 3 3 1 ] [1 4 6 4 1 ] for A = 5

I know, i did not say it was your problem, it's simply a standard warning against something you should not do. — Eregrith
– Eregrith, Commented Jun 2, 2015 at 14:11
What "someone said" was correct but as you go for( j=0; j<=i; j++ ) it must be result[i] = malloc((i+1) * sizeof(int)); — Ingo Leonhardt
– Ingo Leonhardt, Commented Jun 2, 2015 at 14:11

Bathsheba · Accepted Answer · 2015-06-02 14:08:17Z

1

You've allocated memory for the array of rows, but you haven't allocated memory for each row.

Currently result[i] points to unallocated memory.

answered Jun 2, 2015 at 14:08

Bathsheba

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