Question

I have been at this problem for the last 6 hours and have been hitting google like mad to no avail.

Right I need a pointer to an array. This array contains pointers to Linked lists. Im going to have to malloc it since I dont know the array size until runtime.

LList **array

This was my first thought but this just gives me a pointer to an array of LList. Or atleast that is my understanding. Can someone give me a hand?

EDIT: Some info on how it would be used: I am implementing a very basic hash table. There is a structure that contains a pointer to an array of pointers to linked lists.
It needs to be a pointer to the array so that when I resize the table. I can just change the pointer to point to the larger table.

Answer 1

It sounds like you’re on the right track.

LList **array;
array = malloc(num_ptrs * sizeof(LList*));

array is now an array of pointers to LList, and elements such as array[3] will be a pointer to a LList.

Arrays and pointers are very similar in C (but not identical!), as shown by the classic example: *(array + 2) is mostly equivalent to array[2].

Edit:
When you need to resize the table, you’ll just need to realloc the additional space:

LList **new_array;
new_array = realloc(old_array, new_size * sizeof(LList*));

new_array and old_array may or may not be the same pointer afterwards, but either way new_array is guaranteed to be a pointer to enough space to hold the new array (or NULL if the memory couldn’t be allocated)

2nd Edit:
As user411313 alluded, if you want the actual pointer to the array, you’ll need to take the address of the array:

LList ***p_array;
p_array = &array;