Question

Set up graph based on the file input below in .txt

7
Ari
Bob
Chio
Dmitri
Ehab
Gerald
Fritz
Ari Bob
Ari Chio
Bob Ari
Chio Ari
Chio Ehab
Chio Gerald
Dmitri Ehab
Dmitri Gerald
Ehab Chio
Ehab Dmitri
Gerald Chio
Gerald Dmitri
Gerald Fritz
Fritz Gerald

(Should be in display console)

Write a java program to Implementing Graph with Adjacency List:

Expected Result:

Ari-->Bob-->Chio

Bob-->Ari

Chio-->Ari-->Ehab-->Gerald

Dmitri-->Ehab-->Gerald

Ehab-->Chio-->Dmitri

Gerald-->Chio-->Dmitri-->Fritz

Fritz-->Gerald

Answer 1

// Firstly Know the meaning of
Adjacency List:

-> Adjacency List is the Array[] of Linked List, where array
size is same as number of Vertices in the graph.
Every Vertex has a Linked List.
Each Node in this Linked list represents the reference to the other
vertices which share an edge with the current vertex.
The weights can also be stored in the Linked List Node.

// now code

import java.util.LinkedList;

public class Graph {
int vertex;
LinkedList<Integer> list[];

public Graph(int vertex) {
this.vertex = vertex;
list = new LinkedList[vertex];
for (int i = 0; i <vertex ; i++) {
list[i] = new LinkedList<>();
}
}

public void addEdge(int source, int destination){

//add edge
list[source].addFirst(destination);

//add back edge ((for undirected)
list[destination].addFirst(source);
}

public void printGraph(){
for (int i = 0; i <vertex ; i++) {
if(list[i].size()>0) {
System.out.print("Vertex " + i + " is connected to: ");
for (int j = 0; j < list[i].size(); j++) {
System.out.print(list[i].get(j) + " ");
}
System.out.println();
}
}
}

public static void main(String[] args) {
Graph graph = new Graph(5);
graph.addEdge(0,1);
graph.addEdge(0, 4);
graph.addEdge(1, 2);
graph.addEdge(1, 3);
graph.addEdge(1, 4);
graph.addEdge(2, 3);
graph.addEdge(3, 4);
graph.printGraph();
}
}