Question of the Day A friend tells the truth when saying: A road near my house runs directly north-south; I get on the road facing north, drive for a mile, & end up south of where I started How does he do it?

Question of the Day A friend tells the truth when saying: A road near my house runs directly north-south; I get on the road facing north, drive for a mile, & end up south of where I started How does he do it? Note: He (anyone) doesn't live near the north pole

Question of the Day

 Are created using linear sequence of nodes  Each Node contains:  Reference to data (element) stored in Node  Link to next Node in linked list Singly Linked List

Node s Are Not Enough  Node s are workers making linked lists possible  Necessary for the smooth running of linked list  Treated like other jobs smoothing things out  Added & removed as needed  Used only to keep the list running

Node s Are Not Enough

 Node s are workers making linked lists possible  Necessary for the smooth running of linked list  Treated like other jobs smoothing things out  Added & removed as needed  Used only to keep the list running  Never allowed outside of the linked list

Node s Are Not Enough

T removeFirst()

SLinkedList head size  4 SLinkedList head size  3

T removeMiddle(Node prev) SLinkedList head size  4 SLinkedList head size  3

Traversing a List  Often need to go through items in a list  Return element stored by the n th Node  Search and find if element is in list  Count elements larger/smaller/equal than some value  Add an element at list’s end  Cannot do this directly with linked lists  Arrays have brackets, but linked lists use objects  Must traverse list by travelling from Node to Node  Relies heavily on understanding how objects work

void addLast(T el) SLinkedList head size  4 SLinkedList head size  5

 Link to previous node in list also in each node  Each DNode contains:  Element (data) reference  Link to next DNode  Prev(ious) DNode also linked Doubly Linked List elem DNode Instance nextprev

 Link to previous node in list also in each node  Each DNode contains:  Element (data) reference  Link to next DNode  Prev(ious) DNode also linked Doubly Linked List Doubly Linked List With 4 Elements Ø

 Link to previous node in list also in each node  Each DNode contains:  Element (data) reference  Link to next DNode  Prev(ious) DNode also linked Doubly Linked List Sequence of 4 DNode s Ø

 Link to previous node in list also in each node  Each DNode contains:  Element (data) reference  Link to next DNode  Prev(ious) DNode also linked Doubly Linked List & Sentinels Doubly Linked List With 4 Elements & Sentinels Ø Ø

 Link to previous node in list also in each node  Each DNode contains:  Element (data) reference  Link to next DNode  Prev(ious) DNode also linked Doubly Linked List & Sentinels Doubly Linked List With 4 Elements & Sentinels DList head tail size  4 Ø Ø

Doubly Linked List  DNode could extend Node  next & elem fields are needed by both classes  Only difference is prev field added by DNode  DList is not subclass of SList  Both classes define identical methods…  …are entirely different when implemented

 Identical nodes as singly or doubly linked list  This example shows singly linked variety  Reference to first node stored in last node  Notice this becomes a big circle  Now you know idea behind name Circular Linked List BCD head A

Your Turn  Get into your groups and complete activity

For Next Lecture  Read GT3.5 for Wednesday  What is recursion?  Why does recursion rock so much?  How do you write a recursive method?  Week #7 weekly assignment available now  Angel also has programming assignment #1  Pulls everything together and shows off your stuff