How to implement a compact linked list with array?

问题

Here is the question of exercise CLRS 10.3-4 I am trying to solve

It is often desirable to keep all elements of a doubly linked list compact in storage, using, for example, the first m index locations in the multiple-array representation. (This is the case in a paged, virtual-memory computing environment.) Explain how to implement the procedures ALLOCATE OBJECT and FREE OBJECT so that the representation is compact. Assume that there are no pointers to elements of the linked list outside the list itself. (Hint: Use the array implementation of a stack.)

Here is my soln so far

int free; 
int allocate()
{
    if(free == n+1)
        return 0;
    int tmp = free;
    free = next[free];
    return tmp;
}
int deallocate(int pos)
{

    for(;pos[next]!=free;pos[next])
    {
        next[pos] = next[next[pos]];
        prev[pos] = prev[next[pos]];
        key[pos] = key[next[pos]];
    }
    int tmp = free;
    free = pos;
    next[free] = tmp;
}

Now , The problem is , If this is the case , We don't need linked list. If deletion is O(n) we can implement it using normal array. Secondly I have not used the array implementation of stack too . So where is the catch? How should I start?

回答1:

You don't have to shrink the list right away. Simply leave a hole and link that hole to your free list. Once you've allocated the memory, it's yours. So let's say your page size is 1K. Your initial allocated list size would then be 1K, even if the list is empty. Now you can add and remove items very effectively.

Then introduce another method to pack your list, i.e. remove all holes. Keep in mind that after calling the pack-method, all 'references' become invalid.

来源：https://stackoverflow.com/questions/22574182/how-to-implement-a-compact-linked-list-with-array