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CS 307 Fundamentals of Computer Science
Recursive Data Structures
Linked Lists are dynamic data structures
- They grow and shrink one element at a time, normally without some
of the inefficiencies of arrays
Big O of Array Manipulations
- Access the kth element
- Add or delete an element in the middle of the array while maintaining
relative order
- adding element at the end of array? space avail? no space avail?
- add element at beginning of an array
If accesses are all at beginning or end of list, a linked
structure offers improvements
Linked Lists could be used as the underlying storage
container for higher level ADTs (stack, queue)
CS 307 Fundamentals of Computer Science
Nodes and Lists
A different way of implementing a list
Each element of a Linked List is a separate
Node object.
Each Node tracks a single piece of data plus
a reference (pointer) to the next
Create a new Node every time we add
something to the List
Remove nodes when item removed from list
and allow garbage collector to reclaim that
memory
CS 307 Fundamentals of Computer Science
One Implementation of a Linked List
The Nodes shown on the previous slide are
singly linked
- a node refers only to the next node in the
structure
- it is also possible to have doubly linked nodes.
- The node has a reference to the next node in the
structure and the previous node in the structure
as well
How is the end of the list indicated
- myNext = null for last node
- a separate dummy node class / object
CS 307 Fundamentals of Computer Science
A Simple List Interface
public interface IList
void add(Object item);
void add(Object item, int pos);
Object set(Object item, int pos);
void add(List other);
Object get(int pos);
Object remove(int pos);
int size();
CS 307 Fundamentals of Computer Science
Add Element - List Empty (Before)
myHead myTail iMySize
null null 0
Object
item
CS 307 Fundamentals of Computer Science
Add Element - List Empty (After)
myHead myTail iMySize
1
Object
Node
myData myNext
null
CS 307 Fundamentals of Computer Science
Add Element - List Not Empty (After)
2
Object
Node
myData myNext
myHead myTail iMySize
Object
Node
myData myNext
null
CS 307 Fundamentals of Computer Science
Code for default add
public void add(Object item)
CS 307 Fundamentals of Computer Science
Code for get
public Object get(int pos)
CS 307 Fundamentals of Computer Science
Code for remove
public Object remove(int pos)
CS 307 Fundamentals of Computer Science
Remove Back Method
public Object removeBack()
Big O?
CS 307 Fundamentals of Computer Science
Other Possible Features of
Linked Lists
Doubly Linked
Circular
Dummy Nodes for first and last node in list
public class DLNode { private Object myData; private DLNode myNext; private DLNode myPrevious;
CS 307 Fundamentals of Computer Science
Code for arbitrary add -
Doubly Linked List
public void remove(Object item, int pos)
CS 307 Fundamentals of Computer Science
Code for remove
Doubly Linked List
public Object remove(int pos)
