C中基于数组的堆栈实现

Question

I'm referring to this source for array-based implementation of stacks. Somewhere on the page, it says,

Dynamically-sized stack: Now, we will add one more choice to how we'll implement our stack. We want to be able to decide the maximum size of the stack at run-time (not compile-time).

Thus, we cannot use a regular array, but must use a pointer to a dynamically-allocated array.

Now, will we need to keep track of any more information besides the contents and top?

Answer: Yes! We'll need to keep the size of this array, ie, the maximum size of the stack. We'll see why this is necessary as we write the code.

What does it mean to decide the maximum size of the stack at run-time , given the fact that we need to keep the size of the array, ie max size ? we still need the variable that stores the max size of the stack for dynamically allocating memory so I'm not quite sure how this would be beneficial as opposed to having a regular array and declaring capacity(max size) of it.

Answer 1

Because using a dynamically allocated array, you may choose to expand it (allocate a larger array when needed) or to minimize it (free some memory to reduce RAM usage).

What you'd be probably referring to is malloc , realloc and free . What you'd want to do is to allocate some memory using malloc and keep its size in another variable.

When the stack is exhausted (ie the amount of items in it is equal to its size) - you'd want to call realloc to "expand" the array, and update the stack's size.