This is a java program to represent graph as a incidence list. The incidence matrix of G is a n × m matrix (b_{ij}), where n and m are the numbers of vertices and edges respectively, such that b_{ij} = 1 if the vertex v_i and edge x_j are incident and 0 otherwise. If this relationship is represented by a list, list is known as incidence list.
Here is the source code of the Java Program to Represent Graph Using Incidence List. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.
//This is a java program to represent graph as a incidence list
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.LinkedList;
import java.util.Scanner;
public class Represent_Graph_Incidence_List
{
private Map<Integer, List<Integer>> incidenceList;
private int v;
public Represent_Graph_Incidence_List(int vertices)
{
v = vertices;
incidenceList = new HashMap<Integer, List<Integer>>();
for (int i = 1; i <= v; i++)
incidenceList.put(i, new LinkedList<Integer>());
}
public void setEdge(int to, int from, int edge_number)
{
List<Integer> slist = incidenceList.get(to);
slist.add(edge_number);
List<Integer> dlist = incidenceList.get(from);
dlist.add(edge_number);
}
public List<Integer> getEdge(int vertex)
{
return incidenceList.get(vertex);
}
public static void main(String args[])
{
int v, e, count = 1, to, from, edgeNumber;
Scanner sc = new Scanner(System.in);
Represent_Graph_Incidence_List glist;
try
{
System.out.println("Enter the number of vertices: ");
v = sc.nextInt();
System.out.println("Enter the number of edges: ");
e = sc.nextInt();
glist = new Represent_Graph_Incidence_List(v);
System.out
.println("Enter the edges in the graph : <edgenumber> <to> <from>");
while (count <= e)
{
edgeNumber = sc.nextInt();
to = sc.nextInt();
from = sc.nextInt();
glist.setEdge(to, from, edgeNumber);
count++;
}
System.out
.println("The Incidence List Representation of the graph is: ");
System.out.println("Vertex EdgeNumber");
for (int vertex = 1; vertex <= v; vertex++)
{
System.out.print(vertex + "\t:");
List<Integer> edgeList = glist.getEdge(vertex);
for (int j = 1;; j++)
{
if (j != edgeList.size())
System.out.print(edgeList.get(j - 1) + "\t");
else
{
System.out.print(edgeList.get(j - 1));
break;
}
}
System.out.println();
}
}
catch (Exception E)
{
System.out.println("Something went wrong");
}
sc.close();
}
}
Output:
$ javac Represent_Graph_Incidence_List.java $ java Represent_Graph_Incidence_List Enter the number of vertices: 5 Enter the number of edges: 5 Enter the edges in the graph : <edgenumber> <to> <from> 1 1 2 2 2 4 3 5 4 4 4 3 5 5 1 The Incidence List Representation of the graph is: Vertex EdgeNumber 1 :1 5 2 :1 2 3 :4 4 :2 3 4 5 :3 5
Sanfoundry Global Education & Learning Series – 1000 Java Programs.
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