Question

I’m trying to create a bit vector set from a given array. Not sure how to start it off. For example given the array: int rows[] = {1, 2, 5} I need to make a function unsigned short MakeBitVector(int values[], int nValues) You’re allowed to assume that the range for the elements in the array is 1-9. Here’s what I have so far:

unsigned short MakeBitVector(int values[], int nValues)
{
  (55)unsigned short int set = calloc(nValues, sizeof(unsigned short));
  for(int i = 0; i < nValues; i++){
    (57)set[i] = values[i];
  }
  return set;
}

I keep getting warnings and errors:

bits.c:55: warning: initialization makes integer from pointer without a cast

bits.c:57: error: subscripted value is neither array nor pointer

Any ideas on how to fix this?

Answer 1

You definitely need your set to be a pointer:

unsigned short int* set = calloc(nValues, sizeof(unsigned short));

And you have to change the return type of the function to pointer as well.

Edit: if you want to pack everything into one int, you can go on in a simpler way:

unsigned short MakeBitVector(int values[], int nValues)
{
    unsigned short int set = 0;
    for (int i = 0; i < nValues; i++)
        set |= 1 << values[i];
    return set;
}

You don’t need to allocate a single int, returning the copy is just fine.