1. Problem Understanding
Recall
Pseudocode 👍
The ‘Lifecycle’ of a Solution
2 Examples
Notes are available on my webpage now.
Problem Understanding
Design
Pseudocode
Coding
Testing

2. Outline What is a Data Structure Very Fundamental Data Structures
Arrays
What Arrays are good for
What Arrays do poorly
Linked Lists

3. What is a Data Structure
Arrangement or organization of data [in memory or anywhere]
The arrangement is to make something possible or make it easer, faster, or more effecent.

4. Arrays
Array is a sequence of n items of the same data type that are stored contiguously in computer memory and made accessible by specifying a value of the index
Each and every element of an array can be accessed in the same constant amount of time regardless of where in the array the element in question is located.
Length is set in ‘declaration’

5. Arrays An array can store primitive elements, such as characters
An array can also store references to objects

6. Arrays and dynamic scenarios
To add an entry e into array board at index i, we need to make room for it by shifting forward the n - i entries

7. Arrays and dynamic scenarios
To remove the entry e at index i, we need to fill the hole left by e by shifting backward the n - i - 1 elements

8. Dynamic scenarios
So what is good for a changing structure ?
Lists

9. Singly Linked List
A singly linked list is a concrete data structure consisting of a sequence of nodes, starting from a head pointer
Each node stores
element
link to the next node
next
node
element
head  A B C D

10. A Nested Node Class

11. Accessor Methods

12. Inserting at the Head Allocate new node Insert new element
Have new node point to old head
Update head to point to new node

13. Inserting at the Tail Allocate a new node Insert new element
Have new node point to null
Have old last node point to new node
Update tail to point to new node

14. Java Methods

15. Update head to point to next node in the list
Removing at the Head
Update head to point to next node in the list
Allow garbage collector to reclaim the former first node

16. Java Method

17. Removing at the tail of a singly linked list is not efficient!
There is no constant-time way to update the tail to point to the previous node

18. A doubly linked list can be traversed forward and backward
Nodes store:
element
link to the previous node
link to the next node
Special trailer and header nodes
prev
next
element
node
trailer
header
nodes/positions
elements

19. p A B C p q A B C X p q A B X C Insertion
Insert a new node, q, between p and its successor. p A B C p q A B C X p q A B X C

20. A B C D p A B C p D A B C Deletion
Remove a node, p, from a doubly linked list. A B C D p A B C p D A B C

21. Doubly-Linked List in Java
© 2014 Goodrich, Tamassia, Goldwasser

22. Doubly-Linked List in Java, 2
© 2014 Goodrich, Tamassia, Goldwasser

23. Doubly-Linked List in Java, 3
© 2014 Goodrich, Tamassia, Goldwasser

24. Doubly-Linked List in Java, 4
© 2014 Goodrich, Tamassia, Goldwasser

25. Reading
[G] Section 3.1
[G] Section 3.2, 3.3, and 3.4