Computer Science and Software EngineeringUniversity of Wisconsin - Platteville

5. LinkedList

Yan ShiCS/SE 2630 Lecture Notes

Linked List

Unsorted List Sorted List Double linked list Circular linked list

Sorted and Unsorted Lists

UNSORTED LIST

Elements are placed into the list in no particular order.

SORTED LIST

List elements are in an order that is sorted in some way -- either numerically or alphabetically by the elements themselves, or by a component of the element (called a KEY member) .

ADT Unsorted List Operations

Transformers – MakeEmpty – PutItem – DeleteItem

Observers – IsFull– GetLength– GetItem

Iterators – ResetList – GetNextItem

change state

observe state

process all

class UnsortedType<char>

MakeEmpty

~UnsortedType

DeleteItem . . .

PutItem

UnsortedType

GetItem

GetNextItem

‘X’ ‘C’ ‘L’

Private data:

length 3

listData

currentPos ?

Inserting ‘B’ into an Unsorted List

‘X’ ‘C’ ‘L’

Private data:

length 3

listData

currentPos ?

location = new NodeType;

Private data:

length 3

listData

currentPos ?

item

location

‘B’

‘X’ ‘C’ ‘L’

location->info = item ;

Private data:

length 3

listData

currentPos ?

item

location

‘B’

‘B’

‘X’ ‘C’ ‘L’

location->next = listData ;

Private data:

length 3

listData

currentPos ?

item

location

‘B’

‘B’

‘X’ ‘C’ ‘L’

listData = location ;

Private data:

length 3

listData

currentPos ?

item

location

‘B’

‘B’

‘X’ ‘C’ ‘L’

length++ ;

Private data:

length 4

listData

currentPos ?

item

location

‘B’

‘B’ ‘X’ ‘C’ ‘L’

Sorted Type Class Interface Diagram

SortedType class

IsFull

GetLength

ResetList

DeleteItem

InsertItem

MakeEmpty

GetItem

Private data:

length

info [ 0 ] [ 1 ] [ 2 ]

[MAX_ITEMS-1]

currentPos

GetNextItem

InsertItem algorithm for Sorted Array Based List

• Find proper location for the new element in the sorted list.

• Create space for the new element by moving down all the list elements that will follow it.

• Put the new element in the list.

• Increment length.

DeleteItem algorithm for Sorted Array Based List

• Find the location of the element to be deleted from the sorted list.

• Eliminate space occupied by the item by moving up all the list elements that follow it.

• Decrement length.

class SortedType<char>

MakeEmpty

~SortedType

DeleteItem . . .

InsertItem

SortedType

RetrieveItem

GetNextItem

‘C’ ‘L’ ‘X’

Private data:

length 3

listData

currentPos ?

InsertItem algorithm for Sorted Linked List

• Find proper position for the new element in the sorted list using two pointers predLoc and location, where predLoc trails behind location.

• Obtain a node for insertion and place item in it.

• Insert the node by adjusting pointers.

• Increment length.

The Inchworm Effect

Inserting ‘S’ into a Sorted List

‘C’ ‘L’ ‘X’

Private data:

length 3

listData

currentPos ?

predLoc location

moreToSearch

Finding proper position for ‘S’

‘C’ ‘L’ ‘X’

Private data:

length 3

listData

currentPos ?

predLoc location

NULL

moreToSearch true

Finding proper position for ‘S’

‘C’ ‘L’ ‘X’

Private data:

length 3

listData

currentPos ?

predLoc location

moreToSearch true

Finding Proper Position for ‘S’

‘C’ ‘L’ ‘X’

Private data:

length 3

listData

currentPos ?

predLoc location

moreToSearch false

Inserting ‘S’ into Proper Position

‘C’ ‘L’ ‘X’

Private data:

length 4

listData

currentPos

predLoc location

moreToSearch false

‘S’

What is a Circular Linked List?

• A circular linked list is a list in which every node has a successor; the “last” element is succeeded by the “first” element.

External Pointer to the Last Node

Why Circular Linked list?

It doesn’t make any operation much shorter or simpler…

It is useful for applications that require access to both ends of the list.

What is a Doubly Linked List?

• A doubly linked list is a list in which each node is linked to both its successor and its predecessor.

Linking the New Node into the List

Deleting from a Doubly Linked List

What are Header and Trailer Nodes?

• A Header Node is a node at the beginning of a list that contains a key value smaller than any possible key.

• A Trailer Node is a node at the end of a list that contains a key larger than any possible key.

• Both header and trailer are placeholding nodes used to simplify list processing: we never have to handle special cases when inserting/deleting the first/end node.

A Sorted list Stored in an Array of Nodes

An Array with Linked List of Values and Free Space