Code:
package com.executecodes.graph;
import java.util.InputMismatchException;
import java.util.Scanner;
public class UndirectedEulerianCircuit
{
private int[][] adjacencyMatrix;
private int numberOfNodes;
public UndirectedEulerianCircuit(int numberOfNodes, int[][] adjacencyMatrix)
{
this.numberOfNodes = numberOfNodes;
this.adjacencyMatrix = new int[numberOfNodes + 1][numberOfNodes + 1];
for (int sourceVertex = 1; sourceVertex <= numberOfNodes; sourceVertex++)
{
for (int destinationVertex = 1; destinationVertex <= numberOfNodes; destinationVertex++)
{
this.adjacencyMatrix[sourceVertex][destinationVertex] = adjacencyMatrix[sourceVertex][destinationVertex];
}
}
}
public int degree(int vertex)
{
int degree = 0;
for (int destinationvertex = 1; destinationvertex <= numberOfNodes; destinationvertex++)
{
if (adjacencyMatrix[vertex][destinationvertex] == 1
|| adjacencyMatrix[destinationvertex][vertex] == 1)
{
degree++;
}
}
return degree;
}
public int countOddDegreeVertex()
{
int count = 0;
for (int node = 1; node <= numberOfNodes; node++)
{
if ((degree(node) % 2) != 0)
{
count++;
}
}
return count;
}
public static void main(String... arg)
{
int number_of_nodes;
Scanner scanner = null;
try
{
System.out.println("Enter the number of nodes in the graph");
scanner = new Scanner(System.in);
number_of_nodes = scanner.nextInt();
int adjacency_matrix[][] = new int[number_of_nodes + 1][number_of_nodes + 1];
System.out.println("Enter the adjacency matrix");
for (int i = 1; i <= number_of_nodes; i++)
{
for (int j = 1; j <= number_of_nodes; j++)
{
adjacency_matrix[i][j] = scanner.nextInt();
}
}
// make the graph undirected
for (int i = 1; i <= number_of_nodes; i++)
{
for (int j = 1; j <= number_of_nodes; j++)
{
if (adjacency_matrix[i][j] == 1
&& adjacency_matrix[j][i] == 0)
{
adjacency_matrix[j][i] = 1;
}
}
}
UndirectedEulerPath path = new UndirectedEulerPath(number_of_nodes,
adjacency_matrix);
int count = path.countOddDegreeVertex();
if (count == 0)
{
System.out
.println("As the graph has no odd degree vertex, there is at least one Eulerian Circuit.");
}
else if (count == 2)
{
System.out
.println("As the graph as two vertices with odd degree, there is no Eulerian Circuit but at least one Eulerian Path.");
}
else
{
System.out
.println("As the graph has more than two vertices with odd degree, there is no Eulerian Circuit or Eulerian Path.");
}
}
catch (InputMismatchException inputMismatch)
{
System.out.println("Wrong Input format");
}
scanner.close();
}
}
Output:
Enter the number of nodes in the graph
6
Enter the adjacency matrix
0 1 0 0 0 0
1 0 1 1 0 0
0 1 0 0 0 1
0 1 0 0 1 1
0 0 0 1 0 1
0 0 1 1 1 0
As the graph has more than two vertices with odd degree, there is no Eulerian Circuit or Eulerian Path.
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