Java/DataStructures/Graphs/ConnectedComponent.java at master · devil00/Java · GitHub

History

150 lines (128 loc) · 3.43 KB

Raw

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

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());

}

Java/DataStructures/Graphs/ConnectedComponent.java at master · devil00/Java · GitHub

Expand file tree

Breadcrumbs

ConnectedComponent.java

Latest commit

History

Breadcrumbs

ConnectedComponent.java

File metadata and controls