Question

int  ** b;

b = (int **)(new int[5 * 12]);

for (int i = 0; i < 5; i++) {
    for (int j = 0; j < 12; j++) {
        b[i][j] = 0;
    }
} 

I’m getting access violation error in the row b[i][j] = 0;

Where am I doing it wrong?

Answer 1

Since b has type int**, the expression b[i] points to the offset sizeof(int*)*i and (b[i])[j] adds the offset sizeof(int)*j. In total you are accessing a byte at offset sizeof(int*)*i + sizeof(int)*j which is not at all identical to the offset sizeof(int)*(i*j) which would be used to determine the the index in your flat one dimensional array.

You are requesting a one dimensional array but treating it like a two dimensional array. That cannot work. As usual casting is to blame.