Before introducing new material, here are the recursive versions of the
algorithms from the previous day’s notes.
Stacks
A stack is a collection of items into which new items are inserted and from
which items are deleted from only one end, called the top of the stack.
Different implementations are possible; although the concept of a stack is
unique.
Example: Trays in the cafeteria.
Stacks - 1
Data Structures: Stacks
Practice: Create a recursive version of this function to create a linked list
from an array of values. Answer will appear in the next set of notes.
Practice: Create a recursive version of this function to count the nodes in
a linked list. Answer will appear in the next set of notes.
//Copies the contents of an array into a dynamically
//growing list.
struct node *array_to_list (int a[ ], int j, int n)
{
struct node *head;
if ( j >= n) //base case
return NULL;
else
{ head = malloc(sizeof(struct node));
head -> data = a[j];
head ->next = array_to_list(a, j+1, n);
return head;
}
}
//Count the number of nodes in a list
int count(struct node *head)
{
if (head == NULL) //base case
return 0;
else
return (1 + count(head->next));
}
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