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ConnectedComponent.java
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141 lines (118 loc) · 3.93 KB
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package DataStructures.Graphs;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;
/**
* A class that counts the number of different connected components in a graph
*
* @author Lukas Keul, Florian Mercks
*/
class Graph<E extends Comparable<E>> {
class Node {
E name;
public Node(E name) {
this.name = name;
}
}
class Edge {
Node startNode, endNode;
public Edge(Node startNode, Node endNode) {
this.startNode = startNode;
this.endNode = endNode;
}
}
ArrayList<Edge> edgeList;
ArrayList<Node> nodeList;
public Graph() {
edgeList = new ArrayList<Edge>();
nodeList = new ArrayList<Node>();
}
/**
* Adds a new Edge to the graph. If the nodes aren't yet in nodeList, they
* will be added to it.
*
* @param startNode the starting Node from the edge
* @param endNode the ending Node from the edge
*/
public void addEdge(E startNode, E endNode) {
Node start = null, end = null;
for (Node node : nodeList) {
if (startNode.compareTo(node.name) == 0) {
start = node;
} else if (endNode.compareTo(node.name) == 0) {
end = node;
}
}
if (start == null) {
start = new Node(startNode);
nodeList.add(start);
}
if (end == null) {
end = new Node(endNode);
nodeList.add(end);
}
edgeList.add(new Edge(start, end));
}
/**
* Main method used for counting the connected components. Iterates through
* the array of nodes to do a depth first search to get all nodes of the
* graph from the actual node. These nodes are added to the array
* markedNodes and will be ignored if they are chosen in the nodeList.
*
* @return returns the amount of unconnected graphs
*/
public int countGraphs() {
int count = 0;
Set<Node> markedNodes = new HashSet<Node>();
for (Node n : nodeList) {
if (!markedNodes.contains(n)) {
markedNodes.add(n);
markedNodes.addAll(depthFirstSearch(n, new ArrayList<Node>()));
count++;
}
}
return count;
}
/**
* Implementation of depth first search.
*
* @param n the actual visiting node
* @param visited A list of already visited nodes in the depth first search
* @return returns a set of visited nodes
*/
public ArrayList<Node> depthFirstSearch(Node n, ArrayList<Node> visited) {
visited.add(n);
for (Edge e : edgeList) {
if (e.startNode.equals(n) && !visited.contains(e.endNode)) {
depthFirstSearch(e.endNode, visited);
}
}
return visited;
}
}
public class ConnectedComponent {
public static void main(String[] args) {
Graph graphChars = new Graph();
// Graph 1
graphChars.addEdge('a', 'b');
graphChars.addEdge('a', 'e');
graphChars.addEdge('b', 'e');
graphChars.addEdge('b', 'c');
graphChars.addEdge('c', 'd');
graphChars.addEdge('d', 'a');
graphChars.addEdge('x', 'y');
graphChars.addEdge('x', 'z');
graphChars.addEdge('w', 'w');
Graph graphInts = new Graph();
// Graph 2
graphInts.addEdge(1, 2);
graphInts.addEdge(2, 3);
graphInts.addEdge(2, 4);
graphInts.addEdge(3, 5);
graphInts.addEdge(7, 8);
graphInts.addEdge(8, 10);
graphInts.addEdge(10, 8);
System.out.println("Amount of different char-graphs: " + graphChars.countGraphs());
System.out.println("Amount of different int-graphs: " + graphInts.countGraphs());
}
}