Graph Implementation Composite Default Screen Vertex Representation

cs324fig2.cdr Wednesday, September 9, 2020 9:43:17 AM Color profile: Disabled Graphs: The Basics Composite Default screen Implementation [Edge]target vertex

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Representing graphs in computers is not as Representation simple asthe more abstract math and picture representations. How to store in computer memory? Input formats How to inputvertex and edge info?

Vertex Set 2 choices to implement (program) vertex set as a list: linked or indexed. N A vertex may be b a 0 a implemented as record or object a 1 b to store some d b property fields 2 c such as a label. c … c 3 d d …

Quiz What’s the difference … betweenaa set and list? Hint: at least 2.

© 2020 Dr. Muhammad Al-Hashimi KAU CPCS-324 2 cs324fig2.cdr Wednesday, September 9, 2020 9:43:17 AM Color profile: Disabled Graph Implementation Composite Default screen Edge Representation Incident edges

2 choices to implement edges:aa linked list or matrix (next). adjacency list vertex list b N a b c d a d b a d Each vertex stores incident c … a edge info in its own linked list. a ? Exercise Write a formal (math) … specification. Compare to adjacency list.

0 1 1 acdb b 0 0 a 1 1 1 a d 1 b 1 1 c … … c 1 vertex list d 1 1 a b c d b a d … c a d a b … Exercise Write the adjacency matrix. (Label clock- wise, answer last slide.)

Quiz 5 What’s the maximum number of edges possi- ble in this graph? Draw the missing. 1 3

2 4

Exercise f Write an adjacency b list for each graph. Exercise Which one would be a d e g Compare the adjacency list considered sparse? and the adjacency matrix of each shown graph in terms of efficency of: a) storage, c h and b) add/remove edge ops.

Ata minimum, a vertex object contains 2 fields: a Vertex objects label, and an adjacency list reference (=pointer). Lin“aanguage demo ssignment” page adjacent/target node Adjacency lists a b c d b a d Study linked list demo c a d a b Basic graph object Array ofvertex objects , each reference a linked list of target nodes © 2020 Dr. Muhammad Al-Hashimi KAU CPCS-324 6 cs324fig2.cdr Wednesday, September 9, 2020 9:43:17 AM Color profile: Disabled First Graph Object Composite Default screen

vertex list

this.label .adjacent ← null

b 0 a adjacency lists a d 1 b b c d a c … 2 c d a 3 d a Quiz b What does the self var … this refer to in each case? this.verts []

Development environment Javascript, Firefox + Dev Tools

Coding conventions Object and source organization

Code caller (html) page Link “modules”, generate output

Checkpoint 1 expectations First graph object,starter code in “assignment” page Fill in code where indicated Checkupload guide carefully

Weekly workload 2–– 3 hrs/credit, 15 16 credit semester

Vertex objects Language demo in “assignment” page

adjacent/target node Ata minimum, an adjacent/ target node Adjacency lists storesaoftarget vertex a b c d an incident edge, and b a d a reference to next node Study linked list demo c a in a linked list. d a b Basic graph object Array ofvertex objects , each reference a linked list of target nodes © 2020 Dr. Muhammad Al-Hashimi KAU CPCS-324 11 cs324fig2.cdr Wednesday, September 9, 2020 9:43:18 AM Color profile: Disabled Graph Implementation Composite Default screen Edge Implementation

& Figure 3.10 g h A naive implementation

a e Targetvertices can be c f listed in any order, a d b separator maybe comma or similar. j i

0 a c d e 2 3 4 1 b e f 4 5 2 c a d f ? 3 d a c 4 e a b f 5 f b c e 6 g h i Exercise 7 h g i Discuss at least 2 ? disadvantages of the 8 i h j naive input format. 9 j g i Disadvantages

XML-based formats GraphML, GXL <>graph id="G " edgedefault="undirected " node id="n " node id="n1 " edge id="e1 " source=" n " target=" n1 "

v Makkah v1 Jeddah v2 Madinah Plain-text/key-value formats v3 Taif v4 Yanbu N # TGF,LEDA , GML, JSON v v1 79.83 v1 v 79.75 v1 v3 13. v2 v1 38.65

Edge list specification

Re-implement input interface Need edge type specification Some add-edge interface to hide insert detail

adjacency lists this.adjacent ←?

1 b 3 0 a 1 b 2 c 3 d a d 1 b a d c … 2 c a 2 … target nodes

this.verts[]

A minimum target node contains array Simple node index of adjacent vertex. Review linked list package Ñ It’s more important to learn how to use the package at this Note object interfaces stage. Call examples © 2020 Dr. Muhammad Al-Hashimi KAU CPCS-324 15 cs324fig2.cdr Wednesday, September 9, 2020 9:43:19 AM Color profile: Disabled Programming Checkpoint Composite Default screen Checkpoint 2

Clean up needed parts of your code from previous Checkpoint expectations starter file and paste it into the new one. First edge implementation, starter 2 Usenew code starter Fill under outline comments Review upload guide

Answers 1 234 1 2 Demo some basic Git moves 4 3