COSC 1P03

Data Structures and Abstraction 5.1

Linear Linked Structures

A bank is a place where they lend you an umbrella in fair weather and ask for it back when it begins to rain.

Robert Frost (1874-1963)

COSC 1P03

Data Structures and Abstraction 5.2

Dynamic Structures

collections limitations of static structures (i.e. arrays)

fixed size waste space

rearrangement of entries sharing between structures?

dynamic data structures change size over time storage proportional to amount of information

linked structures nodes (objects) connected together by references dynamic allocation/deallocation in array proximity implicit, in linked structure it is

explicit linear linked structures

aka linked lists

COSC 1P03

Data Structures and Abstraction 5.3

Sequentially-linked Structures

each node indicates its successor (via a reference) first node located via reference last node has no successor (null) each node represents one entity empty collection has null reference

COSC 1P03

Data Structures and Abstraction 5.4

Representation

nodes are objects dynamic creation

let entity objects be nodes? add reference field disadvantages

object must “know” it is on list multiple lists must modify class

COSC 1P03

Data Structures and Abstraction 5.5

Node Wrapper Class

separate class references objects wrapper class, mixin

fields reference (p.theStudent) link (p.next)

constructor visibility

class fields

as sequentially-linked structure general case initial (empty) state

multiple lists different sequence of Nodes, same objects

COSC 1P03

Data Structures and Abstraction 5.6

Operations

insertion where?

deletion which node?

traversal “visit” all nodes like array traversal

search special traversal simple vs exhaustive

COSC 1P03

Data Structures and Abstraction 5.7

Insertion

insert where? front end in some order (e.g. sorted)

at front new entry points to previous front list reference points to new entry

pattern O(1)

repeated application reverse order

COSC 1P03

Data Structures and Abstraction 5.8

Deletion

delete which node? first last matching a key

only if not empty delete first

move list pointer to second node garbage collection

node entity

pattern O(1)

COSC 1P03

Data Structures and Abstraction 5.9

Traversal

sequential processing to get to nth node must first get to (n-1)st node

travelling pointer start at first node move to node's successor

p = p.next termination

no more nodes (p == null) pattern

O(n) vs array traversal

sequential traversal pattern

COSC 1P03

Data Structures and Abstraction 5.10

Search

search key two outcomes

success failure

variant of traversal two exits

end of list found item

pattern O(n)

COSC 1P03

Data Structures and Abstraction 5.11

Insertion at End of List

for insertion in order find end of list

traversal 2 travelling pointers

initial stateq is predecessor of p

insert pattern

traverse updating p & q

insert 2 cases

q == null (empty list)q != null (at end)

O(n)

COSC 1P03

Data Structures and Abstraction 5.12

Deletion of Last Node

must modify second last node find second last node

traversal 2 travelling pointers test

pattern pre test

error traverse delete

2 casesq == null (only node)q != null (last node)

O(n)

COSC 1P03

Data Structures and Abstraction 5.33

The End