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Graph TheoryPart One

Graph TheoryPart One

For those of you who have already

completed CS106B/X:

http://strangemaps.files.wordpress.com/2007/02/fullinterstatemap-web.jpg

Chemical Bonds

http://4.bp.blogspot.com/-xCtBJ8lKHqA/Tjm0BONWBRI/AAAAAAAAAK4/-mHrbAUOHHg/s1600/Ethanol2.gif

http://www.prospectmagazine.co.uk/wp-content/uploads/2009/09/163_taylor2.jpg

What's in Common

● Each of these structures consists of● a collection of objects and● links between those objects.

● Goal: find a general framework for describing these objects and their properties.

A graph is a mathematical structurefor representing relationships.

A graph consists of a set of nodes connected by edges.

A graph is a mathematical structurefor representing relationships.

A graph consists of a set of nodes (or vertices) connected by edges (or arcs)

A graph is a mathematical structurefor representing relationships.

A graph consists of a set of nodes (or vertices) connected by edges (or arcs)

Nodes

A graph is a mathematical structurefor representing relationships.

A graph consists of a set of nodes (or vertices) connected by edges (or arcs)

Edges

Some graphs are directed.

On these sites, you can follow someone who doesn’t follow

you back.

A tournament diagram shows who

beat who.

CAT SAT RAT

RANMAN

MAT

CAN

Some graphs are undirected.

Words that differ from each other by exactly

one letter.

On this site, if you are friends with someone, they are also friends

with you.Atoms that are

adjacent to each other in a molecule.

Going forward, we're exclusively focused on undirected graphs.

The term “graph” will mean undirected graphs with a finite number of nodes,

(unless specified otherwise).

Formalizing Graphs

● How might we define a graph mathematically?

● We need to specify● what the nodes in the graph are, and● which edges are in the graph.

● The nodes can be pretty much anything.● What about the edges?

Formalizing Graphs

● An unordered pair is a set {a, b} of two elements a ≠ b. (Remember that sets are unordered).● {0, 1} = {1, 0}

● An undirected graph is an ordered pair G = (V, E), where● V is a set of nodes, which can be anything, and● E is a set of edges, which are unordered pairs of nodes drawn

from V.● [For your reference, but remember we won’t be

focusing on them in this class] A directed graph is an ordered pair G = (V, E), where● V is a set of nodes, which can be anything, and● E is a set of edges, which are ordered pairs of nodes drawn

from V.

● An unordered pair is a set {a, b} of two elements a ≠ b.● An undirected graph is an ordered pair G = (V, E), where

● V is a set of nodes, which can be anything, and● E is a set of edges, which are unordered pairs of nodes drawn from V.

● An unordered pair is a set {a, b} of two elements a ≠ b.● An undirected graph is an ordered pair G = (V, E), where

● V is a set of nodes, which can be anything, and● E is a set of edges, which are unordered pairs of nodes drawn from V.

Answer at PollEv.com/cs103 ortext CS103 to 22333 once to join, then a number.

Answer at PollEv.com/cs103 ortext CS103 to 22333 once to join, then a number.

How many of these drawings are of valid undirected graphs?How many of these drawings are of valid undirected graphs?

A

C

B

D

A

C

B

D

A

C

B

D

A

C

B

D

ABBBC

A

C

B

D

Self-Loops

● An edge from a node to itself is called a self-loop.● In undirected graphs, self-loops are generally not

allowed.● Can you see how this follows from the definition?

● In directed graphs, self-loops are generally allowed unless specified otherwise.

✓×

Standard Graph Terminology

CAT SAT RAT

RANMAN

MAT

CAN

Two nodes are called adjacent if there is an edge between them.

CAT SAT RAT

RANMAN

MAT

CAN

Two nodes are called adjacent if there is an edge between them.

Adjacent nodes

● Let G = (V, E) be a graph.● Intuitively, two nodes are adjacent if they're

linked by an edge.● Formally speaking, we say that two

nodes u, v ∈ V are adjacent if {u, v} ∈ E.

http://strangemaps.files.wordpress.com/2007/02/fullinterstatemap-web.jpg

http://strangemaps.files.wordpress.com/2007/02/fullinterstatemap-web.jpg

SF Sac

Port

Sea But

SLC

Mon

LV

Bar Flag

LA

SD Nog

Phoe

SF Sac

Port

Sea But

SLC

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Bar Flag

LA

SD Nog

Phoe

From

To

SLC

LA

SD

But

Mon

LV

Bar Flag

Nog

Phoe

SF Sac

Port

Sea

From

To

SF, Sac, Port, SeaSF, Sac, Port, Sea

LA

SD

But

Mon

LV

Bar Flag

Nog

Phoe

SLCSF Sac

Port

Sea

From

To

SF, Sac, SLC, Port, SeaSF, Sac, SLC, Port, Sea

SD Nog

Port

SLC

LA

But

Mon

LV

Bar Flag

Phoe

SF Sac

Sea

From

To

SF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, SeaSF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, Sea

SD Nog

Port

SLC

LA

But

Mon

LV

Bar Flag

Phoe

SF Sac

Sea

From

To A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

SF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, SeaSF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, Sea

SD Nog

Port

SLC

LA

But

Mon

LV

Bar Flag

Phoe

SF Sac

Sea

From

To A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, SeaSF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, Sea

SD Nog

Port

SLC

LA

But

Mon

LV

Bar Flag

Phoe

SF Sac

Sea

From

To A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, SeaSF, Sac, LA, Phoe, Flag, Bar, LV, Mon, SLC, But, Sea

(This path has length 10, but

visits 11 cities.)

(This path has length 10, but

visits 11 cities.)

SF Sac

Port

Sea But

SLC

Mon

LV

Bar Flag

LA

SD Nog

Phoe

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SF Sac

Mon

LV

Bar Flag

LA

SD Nog

Phoe

Port

Sea But A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SLC

Sea, But, SLC, Port, SeaSea, But, SLC, Port, Sea

From/To

Flag

SF

SD Nog

Phoe

Sac

Mon

LV

Bar

LA

Port

Sea But A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SLC

Sac, Port, Sea, But, SLC, Mon, LV, Bar, LA, SacSac, Port, Sea, But, SLC, Mon, LV, Bar, LA, Sac

From/To

Flag

SF

SD Nog

Phoe

Sac

Mon

LV

Bar

LA

Port

Sea But A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SLC

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

Sac, Port, Sea, But, SLC, Mon, LV, Bar, LA, SacSac, Port, Sea, But, SLC, Mon, LV, Bar, LA, Sac

From/To

Flag

SF

SD Nog

Phoe

Sac

Mon

LV

Bar

LA

Port

Sea But A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SLC

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

Sac, Port, Sea, But, SLC, Mon, LV, Bar, LA, SacSac, Port, Sea, But, SLC, Mon, LV, Bar, LA, Sac

(This cycle has length nine and visits nine different cities.)

(This cycle has length nine and visits nine different cities.)

From/To

SF Sac

Port

Sea But

SLC

Mon

LV

Bar Flag

LA

SD Nog

Phoe

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Answer at PollEv.com/cs103 ortext CS103 to 22333 once to join, then A, …, or E.

Answer at PollEv.com/cs103 ortext CS103 to 22333 once to join, then A, …, or E.

How many paths in this graphare there from SF to LA?

A. 1B. 4C. 10D. 20E. None of these.

How many paths in this graphare there from SF to LA?

A. 1B. 4C. 10D. 20E. None of these.

SF Sac

Port

Sea But

SLC

Mon

LV

Bar Flag

LA

SD Nog

Phoe

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Sac

Port

Sea But

SLC

Mon

LV

Bar Flag

LA

SD Nog

Phoe

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SF

SFSF

Port

Sea But

SLC

Mon

LV

Bar Flag

LA

SD Nog

Phoe

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SacSF

SF, SacSF, Sac

Port

Sea But

SLC

Mon

LV

Bar Flag

SD Nog

Phoe

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SacSF

LA

SF, Sac, LASF, Sac, LA

Port

Sea But

SLC

Mon

LV

Bar Flag

SD Nog

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SacSF

PhoeLA

SF, Sac, LA, PhoeSF, Sac, LA, Phoe

Port

Sea But

SLC

Mon

LV

Bar

SD Nog

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SacSF

PhoeLA

Flag

SF, Sac, LA, Phoe, FlagSF, Sac, LA, Phoe, Flag

Port

Sea But

SLC

Mon

LV

SD Nog

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SacSF

PhoeLA

FlagBar

SF, Sac, LA, Phoe, Flag, BarSF, Sac, LA, Phoe, Flag, Bar

Port

Sea But

SLC

Mon

LV

SD Nog

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SacSF

PhoeLA

FlagBar

SF, Sac, LA, Phoe, Flag, Bar, LASF, Sac, LA, Phoe, Flag, Bar, LA

Port

Sea But

SLC

Mon

LV

SD Nog

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

SacSF

PhoeLA

FlagBar

SF, Sac, LA, Phoe, Flag, Bar, LASF, Sac, LA, Phoe, Flag, Bar, LA

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Port

Sea But

SLC

Mon

LV

SD Nog

SacSF

PhoeLA

FlagBar

SF, Sac, LA, Phoe, Flag, Bar, LASF, Sac, LA, Phoe, Flag, Bar, LA

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Port

Sea But

SLC

Mon

LV

SD Nog

SacSF

PhoeLA

FlagBar

SF, Sac, LA, Phoe, Flag, Bar, LASF, Sac, LA, Phoe, Flag, Bar, LA

(A path, not a simple path.)

(A path, not a simple path.)

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Port

Sea But

SLC

Mon

LV

SD Nog

SacSF

PhoeLA

FlagBar

SF, Sac, LA, Phoe, Flag, Bar, LASF, Sac, LA, Phoe, Flag, Bar, LA

(This path has length six.)

(This path has length six.)

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Port

Sea But

SLC

Mon

LV

SD Nog

SacSF

PhoeLA

FlagBar

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Port

Sea But

SLC

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac

SacSac

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Port

Sea But

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac SLC

Sac, SLCSac, SLC

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

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Sac, SLC, PortSac, SLC, Port

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Sea But

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac SLC

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Sac, SLC, Port, SacSac, SLC, Port, Sac

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Sea But

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac SLC

Port

Sac, SLC, Port, Sac, SLCSac, SLC, Port, Sac, SLC

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Sea But

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac SLC

Port

Sac, SLC, Port, Sac, SLC, PortSac, SLC, Port, Sac, SLC, Port

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Sea But

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac SLC

Port

Sac, SLC, Port, Sac, SLC, Port, SacSac, SLC, Port, Sac, SLC, Port, Sac

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Sea But

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac SLC

Port

A simple cycle in a graph is cycle that does not repeat any nodes or edges except the first/last node.

A simple cycle in a graph is cycle that does not repeat any nodes or edges except the first/last node.Sac, SLC, Port, Sac, SLC, Port, SacSac, SLC, Port, Sac, SLC, Port, Sac

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

Sea But

Mon

LV

SD Nog

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PhoeLA

FlagBar

Sac SLC

Port

A simple cycle in a graph is cycle that does not repeat any nodes or edges except the first/last node.

A simple cycle in a graph is cycle that does not repeat any nodes or edges except the first/last node.Sac, SLC, Port, Sac, SLC, Port, SacSac, SLC, Port, Sac, SLC, Port, Sac

(A cycle, not a simple cycle.)

(A cycle, not a simple cycle.)

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A cycle in a graph is a path from a node back to itself. (By convention, a cycle cannot have length zero.)

A simple path in a graph is path that does not repeat any nodes or edges.

A simple path in a graph is path that does not repeat any nodes or edges.

The length of the path v₁, …, vₙis n – 1.

The length of the path v₁, …, vₙis n – 1.

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Mon

LV

SD Nog

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PhoeLA

FlagBar

Sac SLC

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A simple cycle in a graph is cycle that does not repeat any nodes or edges except the first/last node.

A simple cycle in a graph is cycle that does not repeat any nodes or edges except the first/last node.Sac, SLC, Port, Sac, SLC, Port, SacSac, SLC, Port, Sac, SLC, Port, Sac

(This cycle has length 6.)

(This cycle has length 6.)

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

Sea But

Mon

LV

SD Nog

SF

PhoeLA

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Sac SLC

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A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

Sea But

Mon

LV

SD Nog

SF

PhoeLA

FlagBar

Sac SLC

Port

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

Sea But

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SD Nog

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PhoeLA

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Sac SLC

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A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

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PortFrom

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A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

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A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

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Two nodes in a graph are called connected if there is a path between them.

Two nodes in a graph are called connected if there is a path between them.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

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Two nodes in a graph are called connected if there is a path between them.

Two nodes in a graph are called connected if there is a path between them.

(These nodes are not connected. No Grand

Canyon for you.)

(These nodes are not connected. No Grand

Canyon for you.)

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

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Two nodes in a graph are called connected if there is a path between them.

Two nodes in a graph are called connected if there is a path between them.

A graph G as a whole is called connected if all pairs of nodes in G are connected.

A graph G as a whole is called connected if all pairs of nodes in G are connected.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

A path in a graph G = (V, E) is a sequence of one or more nodes v₁, v₂, v₃, …, vₙ such that any two consecutive nodes in the sequence are adjacent.

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Two nodes in a graph are called connected if there is a path between them.

Two nodes in a graph are called connected if there is a path between them.

A graph G as a whole is called connected if all pairs of nodes in G are connected.

A graph G as a whole is called connected if all pairs of nodes in G are connected.

(This graph is not connected.)

(This graph is not connected.)

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