2.8 KiB
2.8 KiB
id | title | challengeType | forumTopicId |
---|---|---|---|
587d8256367417b2b2512c77 | Adjacency List | 1 | 301620 |
Description
Graphs can be represented in different ways. Here we describe one way, which is called an adjacency list. An adjacency list is essentially a bulleted list where the left side is the node and the right side lists all the other nodes it's connected to. Below is a representation of an adjacency list.
Node1: Node2, Node3Above is an undirected graph because
Node2: Node1
Node3: Node1
Node1
is connected to Node2
and Node3
, and that information is consistent with the connections Node2
and Node3
show. An adjacency list for a directed graph would mean each row of the list shows direction. If the above was directed, then Node2: Node1
would mean there the directed edge is pointing from Node2
towards Node1
.
We can represent the undirected graph above as an adjacency list by putting it within a JavaScript object.
var undirectedG = {
Node1: ["Node2", "Node3"],
Node2: ["Node1"],
Node3: ["Node1"]
};
This can also be more simply represented as an array where the nodes just have numbers rather than string labels.
var undirectedGArr = [
[1, 2], // Node1
[0], // Node2
[0] // Node3
];
Instructions
Create a social network as an undirected graph with 4 nodes/people named James
, Jill
, Jenny
, and Jeff
. There are edges/relationships between James and Jeff, Jill and Jenny, and Jeff and Jenny.
Tests
tests:
- text: <code>undirectedAdjList</code> should only contain four nodes.
testString: assert(Object.keys(undirectedAdjList).length === 4);
- text: There should be an edge between <code>Jeff</code> and <code>James</code>.
testString: assert(undirectedAdjList.James.indexOf("Jeff") !== -1 && undirectedAdjList.Jeff.indexOf("James") !== -1);
- text: There should be an edge between <code>Jill</code> and <code>Jenny</code>.
testString: assert(undirectedAdjList.Jill.indexOf("Jenny") !== -1 && undirectedAdjList.Jill.indexOf("Jenny") !== -1);
- text: There should be an edge between <code>Jeff</code> and <code>Jenny</code>.
testString: assert(undirectedAdjList.Jeff.indexOf("Jenny") !== -1 && undirectedAdjList.Jenny.indexOf("Jeff") !== -1);
Challenge Seed
var undirectedAdjList = {};
Solution
var undirectedAdjList = {
James: ['Jeff'],
Jill: ['Jenny'],
Jenny: ['Jill', 'Jeff'],
Jeff: ['James', 'Jenny']
};