Adjacency Lists


















How can you implement a directed graph using lists?

	For each node, make a list of adjacent nodes.

What are strengths of the adjacency list implementation of graphs?

	1. Sparse graphs (graphs with few edges) use small space.

	2. Finding the nodes adjacent to a single node is fast/easy.


Classwork

You may work with a partner.
Draw the adjacency list representation for the directed graph.
(graph2.pdf)

	V = { a, b, c, d, e }

	E = { (b,a), (b,c), (b,d), (b,e), (c,b), (d,c), (d,e), (e,a) }

	a---b---c
	 \ / \ /
	  e---d


















How can you implement an undirected graph using adjacency lists?

	Make each edge appear on two lists.


Classwork

You may work with a partner.
Draw the adjacency list representation for the undirected graph.
(graph1.pdf)

	V = { a, b, c, d, e }

	E = { {a,b}, {a,c}, {a,e}, {b,c}, {c,d}, {c,e}, {d,e} }

	a---e
	|\  |\
	| \ | d
	|  \|/
	b---c