Code:
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.Map;
import java.util.Scanner;
import java.util.Stack;
public class StrongConnectedComponents
{
private int leader = 0;
private int[] leader_node;
private int explore[];
private int finishing_time_of_node[];
private int finishing_time = 1;
private int number_of_nodes;
private Stack
private Map
public StrongConnectedComponents(int number_of_nodes)
{
this.number_of_nodes = number_of_nodes;
leader_node = new int[number_of_nodes + 1];
explore = new int[number_of_nodes + 1];
finishing_time_of_node = new int[number_of_nodes + 1];
stack = new Stack
finishing_time_map = new HashMap
}
public void strongConnectedComponent(int adjacency_matrix[][])
{
for (int i = number_of_nodes; i > 0; i--)
{
if (explore[i] == 0)
{
dfs_1(adjacency_matrix, i);
}
}
int rev_matrix[][] = new int[number_of_nodes + 1][number_of_nodes + 1];
for (int i = 1; i <= number_of_nodes; i++)
{
for (int j = 1; j <= number_of_nodes; j++)
{
if (adjacency_matrix[i][j] == 1)
rev_matrix[finishing_time_of_node[j]][finishing_time_of_node[i]] = adjacency_matrix[i][j];
}
}
for (int i = 1; i <= number_of_nodes; i++)
{
explore[i] = 0;
leader_node[i] = 0;
}
for (int i = number_of_nodes; i > 0; i--)
{
if (explore[i] == 0)
{
leader = i;
dfs_2(rev_matrix, i);
}
}
}
public void dfs_1(int adjacency_matrix[][], int source)
{
explore[source] = 1;
stack.push(source);
int i = 1;
int element = source;
while (!stack.isEmpty())
{
element = stack.peek();
i = 1;
while (i <= number_of_nodes)
{
if (adjacency_matrix[element][i] == 1 && explore[i] == 0)
{
stack.push(i);
explore[i] = 1;
element = i;
i = 1;
continue;
}
i++;
}
int poped = stack.pop();
int time = finishing_time++;
finishing_time_of_node[poped] = time;
finishing_time_map.put(time, poped);
}
}
public void dfs_2(int rev_matrix[][], int source)
{
explore[source] = 1;
leader_node[finishing_time_map.get(source)] = leader;
stack.push(source);
int i = 1;
int element = source;
while (!stack.isEmpty())
{
element = stack.peek();
i = 1;
while (i <= number_of_nodes)
{
if (rev_matrix[element][i] == 1 && explore[i] == 0)
{
if (leader_node[finishing_time_map.get(i)] == 0)
leader_node[finishing_time_map.get(i)] = leader;
stack.push(i);
explore[i] = 1;
element = i;
i = 1;
continue;
}
i++;
}
stack.pop();
}
}
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();
StrongConnectedComponents strong = new StrongConnectedComponents(number_of_nodes);
strong.strongConnectedComponent(adjacency_matrix);
System.out.println("The Strong Connected Components are");
for (int i = 1; i < strong.leader_node.length; i++)
{
System.out.println( "Node " + i+ "belongs to SCC"
+ strong.finishing_time_map.get(strong.leader_node[i]));
}
} catch (InputMismatchException inputMismatch)
{
System.out.println("Wrong Input Format");
}
}
}
Output:
Enter the number of nodes in the graph
8
Enter the adjacency matrix
0 1 0 0 0 0 0 0
0 0 0 0 0 0 1 0
0 0 0 1 1 0 0 0
0 1 0 0 0 0 1 0
0 0 0 0 0 0 0 1
1 1 0 0 0 0 0 0
0 0 0 0 0 1 0 0
0 0 1 1 0 0 0 0
The Strong Connected Components are
Node 1 belongs to SCC 2
Node 2 belongs to SCC 2
Node 3 belongs to SCC 8
Node 4 belongs to SCC 4
Node 5 belongs to SCC 8
Node 6 belongs to SCC 2
Node 7 belongs to SCC 2
Node 8 belongs to SCC 8
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