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DirectedWeightedGraph.java
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DirectedWeightedGraph.java
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package graph;
import java.util.*;
public class DirectedWeightedGraph implements WeightedGraph {
private Map<Integer, Set<Edge>> adjacencyList;
private final int noOfVertices;
private final int[] inDegree;
public DirectedWeightedGraph(int noOfVertices) {
this.noOfVertices = noOfVertices;
this.initAdjacencyList(noOfVertices);
this.inDegree = new int[noOfVertices];
}
private void initAdjacencyList(int noOfVertices) {
this.adjacencyList = new HashMap<>();
for (int i = 0; i < noOfVertices; i++) {
this.adjacencyList.put(i, new HashSet<>());
}
}
public Map<Integer, Set<Edge>> getAdjacencyList() {
return adjacencyList;
}
public int getNoOfVertices() {
return noOfVertices;
}
@Override
// Time Complexity: O(1)
public boolean addEdge(int source, int destination, int weight) {
if (!this.validateSourceAndDestination(source, destination)) {
return false;
}
this.inDegree[destination]++;
return this.adjacencyList.get(source).add(new Edge(source, destination, weight));
}
@Override
// Time Complexity: O(V)
public boolean removeEdge(int source, int destination) {
if (!this.validateSourceAndDestination(source, destination)) {
return false;
}
this.adjacencyList.get(source).remove(destination);
return true;
}
private boolean validateSourceAndDestination(int source, int destination) {
if (source < 0 || source >= noOfVertices || destination < 0 || destination >= noOfVertices) {
System.out.println("source or destination is invalid");
return false;
}
return true;
}
@Override
// Time Complexity: O(V)
public boolean hasEdge(int source, int destination) {
if (!validateSourceAndDestination(source, destination)) {
return false;
}
Set<Edge> adjacentVertices = this.adjacencyList.get(source);
for (Edge i : adjacentVertices) {
if (destination == i.getDestination()) {
return true;
}
}
return false;
}
@Override
// Time Complexity: O(1)
public int degree(int node) {
return inDegree[node];
}
@Override
// Time Complexity: O(V)
public List<Edge> adjacent(int node) {
return this.adjacencyList.get(node).stream().toList();
}
@Override
// Time Complexity: O(V + E)
public List<Integer> bfs() {
List<Integer> result = new ArrayList<>();
boolean[] visited = new boolean[this.getVerticesCount()];
for (int i = 0; i < this.getVerticesCount(); i++) {
if (!visited[i]) {
bfs(i, visited, result);
}
}
return result;
}
private void bfs(int source, boolean[] visited, List<Integer> result) {
Queue<Integer> queue = new LinkedList<>();
queue.add(source);
visited[source] = true;
while (!queue.isEmpty()) {
int node = queue.poll();
result.add(node);
for (Edge adj : this.adjacent(node)) {
if (!visited[adj.getDestination()]) {
visited[adj.getDestination()] = true;
queue.add(adj.getDestination());
}
}
}
}
@Override
// Time Complexity: O(V + E)
public List<Integer> dfs() {
// TODO: similar to normal DFS traversal
return null;
}
@Override
public String toString() {
StringBuilder s = new StringBuilder();
for (int i = 0; i < noOfVertices; i++) {
s.append(i).append(": ");
for (Edge j : this.adjacencyList.get(i)) {
s.append(j.getDestination()).append(" ");
}
s.append("\n");
}
return s.toString();
}
@Override
public int getVerticesCount() {
return this.noOfVertices;
}
public static void main(String args[]) {
WeightedGraph g = new DirectedWeightedGraph(4);
g.addEdge(0, 1, 1);
g.addEdge(1, 3, 2);
g.addEdge(1, 2, 3);
g.addEdge(2, 3, 4);
System.out.print(g);
System.out.println(g.adjacent(1));
System.out.println(g.degree(2));
System.out.println("Bfs :" + g.bfs());
}
}