118 lines
4.4 KiB
Java
118 lines
4.4 KiB
Java
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/*This Java program,performs the DFS traversal on the given graph represented by a adjacency matrix to find all the forward edges in a graph.Forward Edges are which point from a node of the tree to one of its descendants.the DFS traversal makes use of an stack.*/
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import java.util.InputMismatchException;
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import java.util.Scanner;
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import java.util.Stack;
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public class ForwardEgde
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{
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private Stack<Integer> stack;
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private HashMap<Integer, Integer> forwardEdges;
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private int adjacencyMatrix[][];
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public ForwardEdge()
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{
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stack = new Stack<Integer>();
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forwardEdges = new HashMap<Integer, Integer>();
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}
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public void dfs(int adjacency_matrix[][], int source)
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{
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int number_of_nodes = adjacency_matrix[source].length - 1;
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adjacencyMatrix = new int[number_of_nodes + 1][number_of_nodes + 1];
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for (int sourcevertex = 1; sourcevertex <= number_of_nodes; sourcevertex++)
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{
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for (int destinationvertex = 1; destinationvertex <= number_of_nodes; destinationvertex++)
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{
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adjacencyMatrix[sourcevertex][destinationvertex] =
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adjacency_matrix[sourcevertex][destinationvertex];
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}
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}
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int visited[] = new int[number_of_nodes + 1];
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int element = source;
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int destination = source;
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visited[source] = 1;
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stack.push(source);
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while (!stack.isEmpty())
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{
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element = stack.peek();
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destination = element;
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while (destination <= number_of_nodes)
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{
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if (adjacencyMatrix[element][destination] == 1 && visited[destination] == 1)
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{
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if (!stack.contains(destination))
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{
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if (element < destination )
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forwardEdges.put(element, destination);
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}
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}
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if (adjacencyMatrix[element][destination] == 1 && visited[destination] == 0)
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{
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stack.push(destination);
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visited[destination] = 1;
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adjacencyMatrix[element][destination] = 0;
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element = destination;
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destination = 1;
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continue;
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}
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destination++;
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}
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stack.pop();
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}
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}
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public void printForwardEdges()
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{
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System.out.println("\nSOURCE : DESTINATION");
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Set<Integer> source = forwardEdges.keySet();
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for (Integer sourcevertex : source)
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{
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System.out.println(sourcevertex + "\t:\t"+ forwardEdges.get(sourcevertex));
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}
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}
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public static void main(String...arg)
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{
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int number_of_nodes, source;
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Scanner scanner = null;
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try
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{
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System.out.println("Enter the number of nodes in the graph");
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scanner = new Scanner(System.in);
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number_of_nodes = scanner.nextInt();
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int adjacency_matrix[][] = new int[number_of_nodes + 1][number_of_nodes + 1];
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System.out.println("Enter the adjacency matrix");
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for (int i = 1; i <= number_of_nodes; i++)
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for (int j = 1; j <= number_of_nodes; j++)
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adjacency_matrix[i][j] = scanner.nextInt();
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System.out.println("Enter the source for the graph");
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source = scanner.nextInt();
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ForwardEdge forwardEdge = new ForwardEdge();
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forwardEdge.dfs(adjacency_matrix, source);
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forwardEdge.printForwardEdges();
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}
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catch(InputMismatchException inputMismatch)
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{
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System.out.println("Wrong Input format");
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}
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scanner.close();
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}
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}
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/*
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Enter the number of nodes in the graph
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4
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Enter the adjacency matrix
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0 1 1 0
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0 0 1 0
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0 0 0 1
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1 0 0 0
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Enter the source for the graph
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1
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The Forward Edges are
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SOURCE : DESTINATION
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1 : 3
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