dijkstra in java code code example
Example: java djikstra's algorithm
import java.util.*;
public class DPQ {
private int dist[];
private Set<Integer> settled;
private PriorityQueue<Node> pq;
private int V;
List<List<Node> > adj;
public DPQ(int V)
{
this.V = V;
dist = new int[V];
settled = new HashSet<Integer>();
pq = new PriorityQueue<Node>(V, new Node());
}
public void dijkstra(List<List<Node> > adj, int src)
{
this.adj = adj;
for (int i = 0; i < V; i++)
dist[i] = Integer.MAX_VALUE;
pq.add(new Node(src, 0));
dist[src] = 0;
while (settled.size() != V) {
int u = pq.remove().node;
settled.add(u);
e_Neighbours(u);
}
}
private void e_Neighbours(int u)
{
int edgeDistance = -1;
int newDistance = -1;
for (int i = 0; i < adj.get(u).size(); i++) {
Node v = adj.get(u).get(i);
if (!settled.contains(v.node)) {
edgeDistance = v.cost;
newDistance = dist[u] + edgeDistance;
if (newDistance < dist[v.node])
dist[v.node] = newDistance;
pq.add(new Node(v.node, dist[v.node]));
}
}
}
public static void main(String arg[])
{
int V = 5;
int source = 0;
List<List<Node> > adj = new ArrayList<List<Node> >();
for (int i = 0; i < V; i++) {
List<Node> item = new ArrayList<Node>();
adj.add(item);
}
adj.get(0).add(new Node(1, 9));
adj.get(0).add(new Node(2, 6));
adj.get(0).add(new Node(3, 5));
adj.get(0).add(new Node(4, 3));
adj.get(2).add(new Node(1, 2));
adj.get(2).add(new Node(3, 4));
DPQ dpq = new DPQ(V);
dpq.dijkstra(adj, source);
System.out.println("The shorted path from node :");
for (int i = 0; i < dpq.dist.length; i++)
System.out.println(source + " to " + i + " is "
+ dpq.dist[i]);
}
}
class Node implements Comparator<Node> {
public int node;
public int cost;
public Node()
{
}
public Node(int node, int cost)
{
this.node = node;
this.cost = cost;
}
@Override
public int compare(Node node1, Node node2)
{
if (node1.cost < node2.cost)
return -1;
if (node1.cost > node2.cost)
return 1;
return 0;
}
}